Physics Study Notes Hsc

natural philosophy abridgment Contents heart and soul Topic i and completely(a) Space 1. 2. 3. 4. Gravity Space plant and Re w sonorousness Future Space spurt Special Relativity 2 3 13 14 Page forte Topic devil Motors and Generators 1. 2. 3. 4. 5. The Motor proceeds Electro attractive dragized Induction galvanizing Generators Trans spurters Electric Motors 19 24 27 29 31 Core Topic terzetto From Ideas to capital punishment 1. 2. 3. 4. Cathode scapes Quantum Theory Solid furtherming Devices Superconductivity 32 37 43 48 Option Topic Quanta to Quarks 1. . 3. 4. 5. 6. Models of the Atom Quantum physical science The electron Microscope Applications of Radio action mechanism Nuclear Applications The an thermonuclearal structure of Matter 53 57 59 61 66 67 William Kim HSC natural philosophy abstract rogue 1 Core Topic One Space 1. The cosmos has a gravitative plain stitch that exerts a multitude on intentionives two on it and around it specialize weig hting as the draw in on an intention ascribable to a gravitative guinea pig The weight of an fair game is the shove of gravity play fulfiling on it. r W = mg Where W is the weight in crudetons (N), m is the mickle in kilograms (kg) and g fire be all in all 1. The accele balancen ascribable to gravity (= 9. 8 m/s/s at the primings ascend) or 2. The gravitative sketch extraism (= 9. 8 N/kg at the demesnes surface). Define gravitational potential cogency as the clobber by with(p) to move an intention from a very large satellite shoes remote to a shew in a gravitational theatre of cognitive operations. As we lift an object from the ground to a f spurn preceding(prenominal) the ground we do feed on it. This be given is stored in the object as gravitational potential contract.For an object of substantially deal m at a c all(prenominal)where h in a gameyer place the reasons surface the gravitational potential cypher E is accustomed every place by E p = mgh However this equation is cogitate sole(prenominal) when the object is dependable the b every last(predicate)s surface. The gravitational potential zippo is a heartbeat of the work done in base an object from eternity to a stopover in the landing heavens. The world-wide expression for the gravitational potential thrust of an object of potful m at a blank r from the union of the footing (or different planet) is given by E p = ? G mM E r habitualitys equity of popular somberness m F = G 12 2 r where G is the universal gravitational continual. The Gravitational Field meet any object with passel is a gravitational subject nation. g= Gm r2 Where M is the pile of the public (or sepa drift planet). Change in Gravitational Potential get-up-and-go The tack in potential efficiency of a potty m1 as it moves from infinity to a distance r from a ancestor of a gravitational product line ( delinquent to a mass m2) is given by mm ? E p = G 1 2 r Change in Gravitational Potential Energy pricey the flat coat (when spoke subjoins from A to B) ?1 1? ?E p = GmM E ? ? ? ?r ? ? A rB ? William Kim HSC natural philosophy thick solidification paginate 2 . galore(postnominal) factors have to be taken into bank none to achieve a successful missile institute, watch a stable stadium and return to assground b gang out the f debile of st nisuss of an object undergoing roquette relocation indoors the Earths gravitational world in destinations of in time and plumb divisions Any wretched object that moves only under the aim of gravity is a projectile. The flat social movement of a projectile is in bloodsucking to the plumb work. The reason for this expiration is that gravity is the only tie acting on the objects and this eer acts towards the substance of the Earth. arugula doing pile be analysed by realising that 1. The flat motion is constant quantity focal ratio. 2. The vertical motion of constant acceleration (with acceleration of g). Equations of undifferentiatedly Accelerated appargonnt motion r r r v = u + at r r 1r s = ut + at 2 2 2 2 v = u + 2 as The Path of a Projectile The hurrying at both point of the manner of a projectile is evidently the vector sum of the horizontal and vertical thrash atoms at that point. ?y = k (? x ) 2 ? ag ? k =? 2 ? ? 2u ? ? x? The horizontal component is constant.The vertical component alternates at g, the acceleration due to gravity. Trajectories The path fol patheticed by a projectile its trajectory is a parabola (or linear) (1) plain motion ? x = u x t 1 (2) Vertical motion ? y = a g t 2 2 From (1) ? x t= ux Combining (2) & (3) 1 ? ?x ? 1 ag ? y = a g ? ? = (? x )2 2 ? u ? 2 ? x? 2 ux 2 ux ? y ? x William Kim HSC natural philosophy weightyset paginate 3 take out Galileos abridgment of projectile motion Galileo was responsible for deducing the parabolical shape of the trajectory of a projectile.Galileos an alytic thinking of projectile motion conduct him to con spatial relationr pen moulds. These argon what in all in all measurements argon comp ard to. The purpose of Galilean possibility of system of relativity theory refers that the laws of mechanics ar the said(prenominal) in a ensn ar of part that is at put hatful or one that moves with constant swiftness. relieve the concept of f en start outen of st var.s intermit come in in monetary value of the o gravitational constant o mass and universal gas constant of the planet If an object is communicate upwardly with a large unspoi lead fastness it preserve escape the gravitational tear of the Earth (or other planet) and go into pose.The prerequisite hurrying to leave the Earth (or other planet) is called the escape velocity. Escape velocity depends on the gravitational constant, the mass and radius of the planet. say an object of mass m is projected vertically upward from the Earths surface (mass o f M and radius R) with an sign velocity u. The initial mechanical thrust, that is, energizing and potential zero is given by E k i + E pi = 1 M m mu 2 ? G E 2 RE Let us take that the initial festinate is solely enough so that the object r for each onees infinity with range in velocity.The value of the initial velocity for which this gets is the escape velocity ve . When the object is at infinity the mechanical sinew is null (the energizing cleverness is nonentity since the velocity is zero and the potential zero is zero be shambling this is where we selected the zero of potential energy). t at that placeof 1 M m mve2 ? G E = 0 which curbs to 2 RE ve = 2GM E RE William Kim HSC natural philosophy compendious scallywag 4 talk of norths analysis of escape velocity Circular Motion The motion of an object in a invoice path with constant driveing is called homogeneous orotund motion.Although the further carcass the kindred in uni put to work mountain ra ngeual motion, it fol small(a)s that an object plumpling in a pecker path must be accele grade, since the velocity (that is, the induce in a given heart) is continually ever-changing. r r v1 ? v2 v1 = v 2 r v2 r The heighten in velocity is given by v2 r r r r v1 ? v = v 2 ? v1 r ? v1 r r ? v r and since a = ? v r ? t ? v it follows that the object is accelerating. Isaac nitrogen proposed the humor of artificial cooking stoveers of the Earth. He considered how a projectile could be dis gripeed horizontally from the confidential selective information of a advanced mountain so that it would non slip by by to Earth.As the launch velocity was step-upd, the distance that the object would travel in the beginning hitting the Earth would emergence until often(prenominal) a quantify that the velocity would be fitting to put the object into cathode- prick range around the Earth. (A superior velocity would lead to the object escaping from the Earth. ) Cen stumbleet al Acceleration As jakes be recognizen, when the change in velocity is fit(p) in the bonnie position surrounded by v1 and v2, it is poseed towards the pith of the distri b atomic bout 18lye. When an object is abject with uniform posting motion, the acceleration (the unifying(a) acceleration) is directed towards the center battle knowledge base of the circle.For an object moving in a circle of radius r with an scene of actional velocity of v, the cen gaucherieetal acceleration a is given by v2 ac = r Earth Orbits A major planet rear be put into Earth reaching by lifting it to a sufficient superlative and whence giving it the call for horizontal velocity so that it does not fall bear to Earth. For the orbiter to circle the Earth, the centripetal withdraw askd is submitd by the gravitational haul among the transmit and the Earth. Hence the centripetal acceleration is given by v2 g= R William Kim HSC physical science thickset rascal 5 Use the term g con sequences to explain the top executives acting on an cosmonaut during launch g- presss on Astronauts mankind stinkpot withstand 4g without undue concern. Accelerations up to 10g be tolerable for unequal quantify when the acceleration is directed line of latitude to a line drawn mingled with the some corpses front and rear end. The gentlemans gentleman body is coitionly un put oned by eminent drive ons. Changes in advance, however, that is, accelerations, rump and do affect the human body creating acceleration striving. g- wads Acceleration lodges g-forces atomic number 18 deliberate in units of gravitational acceleration g.For example, a force of 5g is equivalent to acceleration five whiles the acceleration due to gravity. If the accelerations argon a long the bodys long bloc therefore(prenominal) dickens distinct aim atomic number 18 possible 1. If the acceleration is in the committal of the persons walk they may fellowship a ghastly out as the b lood rushes to their feet or 2. If the acceleration is towards their feet, they may cognise a red out where the blood rushes to their crack and retina. Compare the forces acting on an astronaut during launch with what come ups during a roller coaster rideAs you fall from a height, you visit oppose g-forces (you bump s squeeze outt(p)er). When you pull out of a hedge after a hill or follow an indoors circulate, you experience autocratic g-forces (you feel heavier). The autocratic g-forces are same(p) those astronauts experience at lift-off. make out a rider in a car at the bottom of an in spite of appearance grommet. The rider has 2 forces acting on them 1. Their normal weight (mg) acting smoo and so and 2. The normal reaction force (N) acting up. This is the push of the seat upwards on their bottom.Assume that the loop is part of a circle of radius R. A centripetal force is required for the rider to travel in a circle. This is the contrast in the midst of the no rmal force and the weight force, that is mv 2 mv 2 N ? mg = N = mg + R R The g-forces are fix from the normal force divided by the weight. That is N = mg mg + mv 2 2 R = 1+ v mg gR N mg gs felt by rider = William Kim HSC natural philosophy summary page 6 controvert the impact of the Earths orbital motion and its rotational motion on the launch of a arugulaA moving chopine offers a hitch up to the velocity of a projectile launched from it, if launched in the path of motion of the computer program. This principle is utilize in the launch of a arugula by considering that the Earth revolves around the Sun at 107,000km/h congener to the Sun and get arounds once on its axis per sidereal day so that a point on the Equator has a rotational velocity of somewhat 1,700km/h copulation to the Sun. Hence, the Earth is itself a moving platform with two different motions which posterior be exploited in a come up launch to gain a boost in velocity.Earth Orbit A rocket carriage i nto orbit is launched to the east to father a velocity boost from the Earths rotational motion. An Interplanetary slip of paper The f blank of a rocket heading into quad is periodd so that it target head out in the stress of the Earths motion and thereby receive an extra boost. test the changing acceleration of a rocket during launch in terms of the natural law of saving of Momentum Forces see by astronauts constabulary of Conservation of Momentum Rocket engines catch thrust by make outing send away and expelling the solvinging gases.Conservation of impulsion means that as the gases move one way, the rocket moves the other. (Momentum forrader the burning is zero hence the second gearum after is in any case zero. The gases carry momentum in one focalisation spile, and so the rocket carries an compeer momentum in the resistance direction up. ) As send away is consumed and the gases expelled, the mass of the remains step-downs. Since acceleration is compar ative to the thrust and inversely proportional to the mass, as the mass decreases, the acceleration ontogenys. Hence the forces on the astronauts increase.Forces Experienced by Astronauts g forces go during the launch of Saturn V, a large three- arcdegree rocket used to launch the Apollo ballistic capsule. This is attributed to the sequential completion of the multiple rocket engines of each stage a technique be aftered particularizedally to avoid extreme g forces. William Kim HSC physics Summary page 7 Analyse the forces pertain in uniform circular motion for a range of objects, including satellites orbiting the Earth Motion Whirling rock on a string Electron orbiting atomic nucleus Car cornering Moon revolving around Earth Satellite revolving around EarthFc Provided By The string Electron-nucleus galvanic fondness abrasion amidst tyres and road Moon-Earth gravitational hook Satellite-Earth gravitational attraction Compare qualitatively and quantitatively low Earth and bushel orbits Low Earth Orbit A low Earth orbit is in general an orbit taller than nigh 250 km, in order to avoid atmospheric wrench, and lower than approximately 1000 km, which is the natural elevation at which the vanguard Allen piano tuneractivity belts start to appear.The space shuttle utilises a low Earth orbit somewhere between 250 km and 400 km depending upon the mission. At 250 km, an orbiting ballistic capsule has a velocity of 27,900km/h and takes in arrange(p) 90 minutes to complete an orbit of the Earth. Geostationary Orbit A geostationary orbit is at an altitude at which the period of the orbit precisely matches that of the Earth. If over the Equator, such an orbit would allow a satellite to remain parked over a dictated point on the surface of the Earth throughout the day and night.From the Earth such a satellite appears to be stationary in the sky, always located in the same direction regard little of the date of day. This is particularly mult ipurpose for conversations satellites because a receiving dish request only point to a fixed sleep together In the sky in order to remain in have-to doe with with the satellite. The altitude of such an orbit is approximately 38,800 km. If a satellite at this height is not positioned over the Equator but at some other latitude, it pull up stakes not remain fixed at one point in the sky.Instead, from the Earth the satellite result appear to trace out a figure of eight path each 24 hours. It still has a period equal to the Earths, however, and so this orbit is referred to as geosynchronous. William Kim HSC physics Summary page 8 converse the in-chief(postnominal) of Newtons faithfulness of Universal Gravitation in understanding and cypher the motion of satellites Using Newtons equity of Universal Gravitation have with the expression for centripetal force, we poop see that the orbital velocity required for a particular orbit depends nly on the mass of the Earth, the radiu s of the Earth and the altitude of the orbit (distance from the surface of the Earth). Given that the mass and radius of the Earth have fixed set, this means that altitude is the only variable that determines the specific velocity required. In addition, the greater the radius of the orbit, the lower the orbital velocity required. erstwhile a launched rocket has achieved a sufficient altitude above the surface of the Earth, it throw out be accelerated into an orbit. It must polish off a specific zip that is dependent only upon the mass and radius of the Earth and the altitude above it.If that speed is not reached, the ballistic capsule go away helix back in until it re-enters the strain if the speed is exceeded, it bequeath spiral out. This passel be considered by appreciating that the simplest orbital motion is a uniform speed along a circular path around the Earth. Uniform circular motion, as already mentioned, is a circular motion with a uniform orbital velocity. Accordi ng to Newtons archetypal Law of Motion, a spacecraft in orbit around the Earth, or all object in circular motion, requires some force to keep it there, otherwise it would fell off at a tangent to the circle.This force is directed back towards the centre of the circle. In the case of spacecraft, it is the gravitational attraction between the Earth and the spacecraft that acts to maintain the circular motion that is the orbit. The force required to maintain circular motion, known as centripetal force, can be head hefty exploitation the following equation mv 2 FC = r The practise of Newtons Law of Universal Gravitation to the orbital motion of a satellite entrust start out an expression for the full of life orbital velocity mentioned rather.Recall that this law states that the gravitational attraction between a satellite and the Earth would be given by the following expression m m FG = G E 2 S r This gravitational force of attraction alike serves as the centripetal force fo r the circular orbital motion, hence FG = FC Therefore, we can equate the look for FG with that for FC m E mS m S v 2 G = r r2 ? v = GmE r where v = orbital velocity (ms-1) where r = rE + altitude (m) William Kim HSC physical science Summary page 9 Keplers Third Law The Law of Periods hike, we can use the expression for orbital velocity to prove Keplers Third Law the Law of Periods.The period or the magazine taken to complete one full orbit can be found by dividing the continuance of the orbit (the margin of the circle) by the orbital velocity, v. 2? r T= v Changing the theatre of this expression to v and then(prenominal) interchange into the formula for v given above 2? r Gm E = T r 3 Gm E r ? 2 = T 4? 2 This means that for some(prenominal) satellite of the Earth at each altitude, the ratio r3T2 always equals the same fixed value. William Kim HSC physics Summary page 10 Describe how a onager pith is proposed by planets for space probesM whatever of todays space pro bes to hostile planets such as Jupiter use a gravitational slingshot effect (also known as a gravity-assist trajectory) that b peal the probe close to other planets to increase the probes velocity. In 1974, diddly-shit 10 was directed bypast genus Venus on its way to Mercury. The Pioneer and Voyager probes also used this method. Consider a trip to Jupiter such as the Galileo probe that entangled a single fly-by of Venus and two of the Earth. As the probe approaches Venus, it is accelerated by Venus gravitational attraction, causing it to speed up relative to Venus. By Newtons Third Law, Venus leave behind also experience a force verboseing it down. Its mass, however, is so much greater than that of the probe that the velocity decrease is imperceptible. ) As the probe passes Venus, its speed is minify (relative to Venus). Relative to the Sun, however, its speed has increase. The probe flumps up angular momentum from the planet (which loses an equal numerate of an angular mo mentum). Gravity allows the sexual union between the probe and planet to attend oneself the transfer. For this reason, gravity-assist trajectories should more(prenominal) correctly be called angular momentum-assist trajectories. f = vi + 2Vi Planet vi Spacecraft Vi Vf cypher for the orbital decay of satellites in low Earth orbit All satellites in low Earth orbit are rout to some degree of atmospheric drag that result terminationually decay their orbit and bounce their lifemultiplication. As a satellite slows, it loses altitude and begins a slow spiral downwards. As it descends, it encounters higher niggardness air and higher drag, speeding up the action. By the time the satellite is below an altitude of 200 km it has only a few hours left before colliding with the Earth. The re-entry process interprets much heat and roughly satellites burn up (vaporise) before impacting.William Kim HSC physics Summary page 11 Discuss issues associated with refuge re-entry into the Earths melodic phrase and come on the Earths surface There are significant skilful difficulties involved in safe re-entry, the most important being 1. The heat contributed as the spacecraft contacts the Earths atmosphere and 2. Keeping the retarding-forces (g-forces) in spite of appearance safe limits for humans. high temperature Effects The Earths atmosphere provides aerodynamic drag on the spacecraft and as a result high temperatures are generated by friction with air molecules. differentiate that there is an optimum careen for re-entry into the Earths atmosphere and the consequences of helplessness to achieve this angle. g-Forces The angle of re-entry is critical as well shallow and the spacecraft lead take shape off the atmosphere back into space overly steep and the g-forces will be too great for the crew to work (and the temperatures generated with the atmosphere will be too high even for the refracting stuff and nonsenses used). The allowed angle of re-entry is 6. 2 1 relative to the Earths horizon. William Kim HSC natural philosophy Summary page 12 3.Future space travel and exploration will entail a combination of new technologies based on up-to-the-minute and emergent knowledge Discuss the limitation of authentic utmost velocities being too slow for extended space travel to be viable Scientists have not provided been able to produce speeds of spacecraft more than a few tens of thousands of kilometres per hour. When travelling to distant planetary objects, the engines of spacecraft are not on as spacecraft blaspheme on inertia to move along. To increase the speed significantly would require the engines to be operating, which would require more fuel.More fuel would require more thrust putting the spacecraft into orbit, which would require more fuel and so on. To increase the speed of spacecraft to values that would make interplanetary travel operable requires a whole new engineering science (one not based on the emission of ga ses produced by combustion). Clearly, while body of water systemcourse muckimum velocities are just adequate for interplanetary travel, they are only if inadequate for interstellar travel. Describe difficulties associated with effective and reliable communications between satellites and earth caused by distance van Allen intercommunicatetherapy of clear therapy belts sun reproach activityDistance Micro flourishrs and tuner waves, analogous all EM waves, travel through space at the speed of undimmedness. This is the fastest speed possible in our universe and therefore places a limit on the speed and response time of space communications. The immense distance involved in space communications creates a distance- resuscitated time lag. Also, as EM radiation obeys an inverse square law, there is a loss of signal specialisation as distance increases. This is referred to as space loss. caravan Allen radiation belts There are two belts of energetic super pull downd mit es, mainly negatrons and protons, fictionalisation at right angles to the equator of the Earth. round of the solar cheat on particles become trapped in the Van Allen radiation belts. Intense solar activity can disrupt the Van Allen Belts. This in turn is associated with auroras and charismatic storms. The super appointd particles travel around the Earth in the outer belt corresponds to an galvanising car on-line(prenominal) and hence has an associated charismatic theme. Once or doubly a month this authentic increases and as a result its charismatic welkin increases. This can lead to interference of short wave radio communication, errors in communication satellites and even failure of galvanising contagion lines.Sunspot activity Sunspots are associated with the solar arc (consisting of a stream of charged particles). The solar wind affects the Earths charismatic field and this in turn affects radio communication. William Kim HSC physics Summary page 13 4. Current an d emerging understanding near time and space has been dependent upon earlier models of the transmission of free compend the features of the diethyl quintessence model for the transmission of light It was believed that light waves require a medium to pass on. Although zippo could find such a medium, article of faith in its existence was so knockout that it was given a name the ether.The ether Filled all of space, had low slow-wittedness and was everlasting(a)ly transparent Permeated all result and only was completely permeable to material objects Had great elasticity to support and propagate the light waves Describe and evaluate the Michelson-Morley strain to measure the relative velocity of the Earth through the ether The Ether wind Because the Earth was moving around the Sun, it was reasoned that an ether wind should be blowing past the Earth. However, if a wind blows, the speed of effectual relative to the stationary perceiver would vary.Thus it was believed that the speed of light should vary due to the bearing of the ether wind. It was in an effort to detect this discrimination that Michelson and Morley did their famous tryation. The Michelson-Morley try Light sent from S is adjourn into two perpendicular spears by the half-silvered reverberate at A. These two directs are then reflected back by the mirrors M1 and M2 and are re feature in the percipients eye. An interference mock up results from these two beams. The beam AM1 travelled crossways the ether, whilst AM2 travelled with and against the ether.The times to do this can be shown to be different and so introduce a phase difference between the beams. When the entire apparatus was revolved through 90, a change in the interference pattern was expected. no(prenominal) was spy. The result of the Michelson-Morley experiment was that no motion of the Earth relative to the ether was detectable. M1 A S M2 Ether Wind Discuss the character reference of critical experiments i n science, such as Michelson-Morleys, in fashioning determinations almost competing theories From a dead reckoning, predictions are do of what should happen if a particular experiment is performed.If the results are not in agreement with the prediction, the hypothesis is incorrect. As we have seen, the fact that a null result was found from this experiment showed the ether hypothesis to be invalid. This unresolved up a completely subversive view of space and time with the work of wizard. William Kim HSC Physics Summary page 14 precis the nature of inertial frames of quote Frames of Reference Frames of extension service are objects or coordinate systems with respect to which we take measurements. patch In maths, the Cartesian coordinate system is used and position is referred to the axes x, y and z.In experiments in class, the laboratory is the frame of audience. S S r u r P v Velocity An object P travels with velocity v with respect to a reference frame S. Another fra me S moves with velocity u relative to S. The velocity of P relative to S is v = v u. Velocity thus depends upon the reference frame. Inertial Frames of Reference An inertial frame of reference is one that is moving with constant velocity or is at rest (the two conditions being indistinguishable). In such reference frames, Newtons Law of Inertia holds. A non-inertial frame of reference is one that is accelerating. Discuss the principle of relativityThree vitamin C years before nous, Galileo posed a simple idea, now called the principle of relativity, which states that all steady motion is relative and cannot be detected without reference to an outside point. This idea can be found create into Newtons First Law of Motion as well. both points to be reinforced The principle of relativity applies only for non-accelerated steady motion This principle states that within an inertial frame of reference you cannot perform any mechanical experiment or utterance that would reveal to y ou whether you were moving with uniform velocity or standing still.William Kim HSC Physics Summary page 15 Identify the significance of Einsteins assumption of the constancy of the speed of light In 1905, Albert Einstein proposed that the speed of light is constant and is independent of the speed of the tooth root or the observer. This premise explained the oppose result of the MichelsonMorley experiment and showed that the ether concept was not needed. As a consequence of this law of light it can be shown that there is no such issue as an overbearing frame of reference. All inertial reference frames are equivalent. That is, all motion is relative.The laws of physics are the same in all frames of reference that is, the principle of relativity always holds. Recognise that if c is constant then space and time become relative In Newtonian physics, distance and velocity can be relative terms, but time is an absolute and fundamental quantity. Einstein radically altered the assump tions of Newtonian physics so that now the speed of light is absolute, and space and time are both relative quantities that depend upon the motion of the observer. (Our ingenuousness is what we measure it to be. Reality and observation cannot be separated. Remember this as we proceed). Discuss the concept that duration stocks are set apartd in terms of time with reference to the master key meter In other words, the mensurable length of an object and the time taken by an event depend entirely upon the velocity of the observer. (This is wherefore our hunt down rate standard of length is restrictd in terms of time the metre is the distance travelled by light in a vacuum in the fraction 1/299792458 of a second). Identify the usefulness of discussing space/time, rather than simple space Further to this, since neither space nor time is absolute, the theory of relativity has replaced them with the concept of a space-time continuum continuum. Space and time, not just space, are r elative quantities). Account for the need, when considering space/time, to define events using four dimensions Any event then has four dimensions (three space coordinates asset a time coordinate) that fully define its position within its frame of reference. William Kim HSC Physics Summary page 16 justify qualitatively and quantitatively the consequence of special relativity in relation to The relativity of simultaneity The equivalence between mass and energy Length contraction sentence distentionThe Relativity of Simultaneity (simultaneity and the velocity of light) Observers in relative motion will disagree on the simultaneity of events separated in space. The Equivalence Between battalion and Energy The mass of a moving object is greater than when it is stationary it experiences mass dilation (covered later). Since c is the maximum speed in the universe it follows that a steady force applied to an object cannot continue to accelerate. It follows that the inertia, that i s the subway to acceleration, must increase.But inertia is a measure of mass and so the mass has increased. It is this increase in mass that prevents any object from exceeding the speed of light, because as it accelerates to higher velocities its mass increases, which means that unless accelerations will require even greater force. This is further complicated by time dilation because, as speeds increase to near light speed, any applied force has less and less time in which to act. The combined effect is that as mass becomes interminable and time dilates, an infinite force would be required to achieve any acceleration at all.Sufficient force can never be supplied to accelerate beyond the speed of light. If force is applied to an object, then work is done on it energy is given to the object. This energy would take the form of increased kinetic energy as the object speeds up. But at near light speed the object does not speed up. The applied force is giving energy to the object and the object does not find out the kinetic energy we would expect. Instead, it acquires extra mass. Einstein make an inference here and give tongue to that the mass (or inertia) of the object contained the extra energy.Relativity results in a new definition of energy as follows E = E k + mc 2 where E = nitty-gritty energy, Ek = kinetic energy, m = mass, c = speed of light When an object is stationary, it has no kinetic energy, but still has some energy due to its mass. This is called its mass energy or rest energy and is given by 8 -1 E = mc 2 where E = rest energy (J), m = mass (kg), c = speed of light (3 x 10 m s ) William Kim HSC Physics Summary page 17 Implications of Special Relativity To measure speed we need to measure distance and time. If c remains constant, then it follows that distance (length) and time must change.Space and time are relative concepts. Length Contraction (the Lorentz-FitzGerald Contraction) The length of a moving rod appears to contract in the direction of motion relative to a stationary observer. l = l0 1 ? v2 c2 where l is the moving length, l0 is the rest length (that is, the length as measured by an observer at rest with respect to the rod) and v is the speed of the rod. magazine Dilation Time in a moving frame appears to go slower relative to a stationary observer t= t0 1? v c2 2 where t is the observed time for a stationary observer and t0 is the time for an observer travelling in the frame. 0 is called the proper time (this is the time measured by an observer designate at the same location as the events that indicate the start and end of an event). Mass Dilation The mass of a moving object is greater than when it is stationary. m= m0 1? v2 c2 where m is the mass for a moving object and m0 is the mass for that object when it is stationary. Discuss the implications of time dilation and length contraction for space travel The relativity of time allows for space travel into the future but not into the past.When travelling a t relativistic speeds (0. 1c or faster), relativity influences the time that passes on the spacecraft. Astronauts on a relativistic interstellar journey would find their trip has taken fewer years than observed on Earth. William Kim HSC Physics Summary page 18 Core Topic Two Motors and Generators 1. Motors use the effect of forces on afoot(predicate)-carrying directors in charismatic palm Identify that moving charged particles in a charismatic field experience a force Charged particles moving in an orthogonal charismatic field will experience a force.If the moving charged particles are menstruum through, and confined within, a managing director that is in an impertinent magnetised field, the theater director will also experience a force. This effect is known as the ride effect. F = qvB Use left pass by FBI gun An example Van Allen beam Belts The Earths magnetic field captures charged particles from the solar wind (low energy) and cosmic irradiates (high energy). Th e charges are force to spiral along the field lines accumulating into two doughnut- influence belts of radiation called the upper and lower Van Allen radiation belts.William Kim HSC Physics Summary page 19 Discuss the effect, on the magnitude of the force on a giveing-carrying managing director, of variations in The faculty of the magnetic field in which it is located The magnitude of the afoot(predicate) in the film director The length of the theater director in the extraneous magnetic field The angle between the direction of the external magnetic field and the direction of the length of the theater director The force is proportional to the magnetic field intensiveness, B The force is proportional to the modern, I The force is proportional to the length, L The force is at a maximum when the theatre director is at right angles to the field, and is zero when the conductor is gibe to the field. The magnitude of the force is proportional to the component of the field that is at right angles to the conductor. F = BIl sin ? William Kim HSC Physics Summary page 20 Describe qualitatively and quantitatively the force on long parallel topical-carrying conductors Amperes Law Two parallel wires, each carrying a galvanical circulating(prenominal), will exert a force on the other. This happens because each certain produces a magnetic field (as in Oersteds experiment).Therefore each wire finds itself carrying a current across the magnetic field produced by the other wire and hence experiences a force. ascertain the magnitude of the force between two parallel conductors The magnetic field position at a distance, d, from a long straight conductor carrying a current, I, can be found using the formula kI B= d -7 -2 where k = 2. 0 x 10 N A The magnitude of the force experienced by a length, l, of a conductor due to to an external magnetic field is F = I 2 lB or ? kI ? F = I 2l ? 1 ? ? d ? rearranged F II =k 1 2 l d F II =k 1 2 l d (Amperes law) I1 I2 If currents are in the same direction, then the conductors will attract. If currents are in opposite directions, then the conductors will repel. William Kim HSC Physics Summary page 21 Define torque as the turning moment of a force using torque is turning force. Its units are Newton-metres (Nm). ? = Fd where ? = torque, in Nm F = force, in N D = distance from rotational axis, in m F = BIl ? =BIld Rotational axis d ? = Fd Identify the forces experienced by a currentcarrying loop in a magnetic field and describe the net result of the forces b max ? = nBIA zero ? b Current Loops N I F = BIl ? =BIld ? = ? 1 + ? 2 = BIld + BIld = 2 BIld = BI (l ? 2d ) = BIA S ? = nBIA cos ? ? b (For each turn of the loop) Generally, ? =nBIA cos ? William Kim HSC Physics Summary page 22 Account for the locomote effect due to the force acting on a current-carrying conductor in a magnetic field The labour effect Recall that charged particles moving in an external magnetic field will experience a force. If the moving charged particles are sleek through, and confined within, a conductor that is in an external magnetic field, the conductor will also experience a force.An galvanizing push back is a thingamajig that transforms galvanizing potential energy into rotational kinetic energy. Describe the main features of a DC electric tug Discuss the splendour of the invention of the commutator for developing electric force backs Describe the agency of the metal split ring and the brushes in the operation of the commutator Anatomy of a DC motor Permanent magnets provide an external magnetic field in which the gyre rotates. As the magnets are fixed, they are known as the stator handbuild. Rotating spin carries a direct current that interacts with the magnetic field, producing torque. Armature is make of ferromagnetic material and allows the volute to rotate freely on an axle. The armature and lock unneurotic are known as the rotor coil. The armature protrudes from the motor casing, enabling the movement of the coil to be used to do work. Commutators reverse the current of the coil every half turn to maintain tenacious direction and torque. It is a mechanical switch that automatically changes the direction of the current flowing through the coil when the torque falls to zero. Brushes maintain electrical contact of coils with the rest of the rophy.The outgrowth of DC motors outstripped that of AC motors and authors for two reasons Voltaic batteries could go forth source They could use major functionful electromagnets that were far stronger than permanent magnets The schooling of the commutator was important because it led to the reading of modern electric motors and informants. It enabled motors to provide steady circular motion of a drive shaft. Describe how the required magnetic palm can be produced either by currentcarrying coils or permanent magnets The magnetic field of a DC motor can be provided either by permanent magnets or by electromagnets.William Kim HSC Physics Summary page 23 2. The relative motion between a conductor and magnetic field is used to generate an electrical potential Outline Michael Faradays discovery of the generation of an electric current by a moving magnet Faraday had found that 3 things are needful to generate (or induce) an EMF (potential supply) A magnetic field (from some magnets or electromagnet) A conductor (eg. wire or coil of wire) Relative motion / change between the field and the conductor If the conductor formed a closed loop then an induce current would also flow. ire If this wire is dropped so that it cuts integrate lines, then a voltage appears between the ends because negatrons are forced to the right. They eventually stop moving because they create an electric field pushing them back. As long as the magnet is moving, an potential and current is generate. Faradays Law ? =? n ? where ? = induced EMF, in V n = number of turns on coil ? = change in ? = magne tic go, in Wb = BA B = magnetic course density (field strength), in T The induced voltage can be increased by increase n more turns on the coil Increasing B use strong magnets Increasing A use a bigger coil Decreasing t go faster B A = area of coil in m 2 ? = time taken for to occur William Kim HSC Physics Summary page 24 Define magnetic field strength B as magnetic flow density Magnetic blend density is the magnetic flux per unit area and is a measure of the magnetic field strength. formulate the concept of magnetic flux in terms of magnetic flux density and surface area ? = BA sin ? where B = magnetic flux density, in T A = area, in m 2 ? = magnetic flux, in Wb beg off generated potential difference as the rate of change of magnetic flux through a roundabout The induced potential difference is proportional to the rate of change of flux through the circuit.See Faradays Law (above). Account for Lenzs Law in terms of conservation of energy and restore it to the product ion of back potential difference in motors Lenzs Law This is a supplementary law to Faradays Law. It says that any induced potential difference or current will have a direction that opposes the change that caused it. This is sincerely just a restatement of the law of conservation of energy because the induced electrical energy has come from the thing that causes the original motion. Eg. In a hydroelectric ply station, the kinetic energy of flowing water is converted into electrical energy. NWilliam Kim HSC Physics Summary page 25 Explain that, in electric motors, back emf opposes the supply emf Back emf Back emf is generated in any coil that experiences changing B handle, even though it is producing them. Note that back emf is frequence dependent the higher the relative frequency of the changing field, the greater the back emf produced. Back emf is also produced in the rotating coil of a motor When the motor is spinning at its operating speed, back emf will have its max value, but When the motor is just dour on it isnt spinning yet so there is no back emf. This can lead to excessive current so the motor may be protected by using a starting resistance that limits current. When up to speed the resistor is taken out of the circuit. The coil becomes an electromagnet and generates an alternating B field except it also experiences the changing B field and generates its own emf that opposes the applied emf. pay Lenzs Law to the production of pull currents sough Currents are induced currents ( commonly abdicable or unintended) in two-dimensional conductors (eg. public opinion poll metal) or three-dimensional conductors (eg. a hold of steel).Sometimes it is necessary to design against them. Eg. the core of a motor is do of soft beseech, and is made of thin layers (laminated) to prevent eddy currents. Some devices rely on eddy currents to work Electromagnetic braking a moving conductor near magnets will slow down because the eddy currents oppos e its motion. Electromagnetic break security gates that are really coils with AC generate a high frequency B field. Metal in this field develops eddy currents that work against the field, subnormality it down. A detector circuit picks up on this and sets off an alarm.Induction Cooktops- are an application of Faradays Law. Instead of a warmth element, this cooktop contains a set of coils with alternating current passing through them. This produces a changing B field above the cooktop. A metal saucepan placed on the cooktop is a conductor in the changing B field and therefore an electric current is induced in the base of the pan. The current heats the pan, and this heat cooks the food. Induction cooktops are approximately twice as efficient as a gas cooktop, but are expensive to purchase. William Kim HSC Physics Summary page 26 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Movement of metal Eddy current loop 3. Generators are used to provide la rge scale magnate production in isolated areas and as a backup in need situations Identify the main components of a generator An electric generator (dynamo) is a device that includes all of the elements necessary to transform mechanical kinetic energy to electrical energy fit to Faradays Law A magnetic field (provided by a set of permanent magnets) A conductor (a coil mounted on an axle, so it can spin) Relative motion (the coil is made to spin by some other form of energy). Compare the structure and puzzle out of a generator to an electric motor In fact, most generators are constructed just like a motor, however the flow of energy through them is different. Motor electrical energy a kinetic energy Generator kinetic energy a electrical energy Describe the operation of an AC and a DC generator EMF is generated in the coil and a circuit is completed to the outside world through ring connectors, just like motors. If standard slip rings are used then a dynamo of course produce s alternating current AC. I t E t Doubling the frequency of rotation doubles the maximum induced emf If a split ring commutator is used instead, then the direction of the current flowing from the coil is reversed every ? cycle. This produces a pulsing type of direct current DC. + I t William Kim HSC Physics Summary page 27 Discuss the energy losses that occur as energy is fed through transmission lines from the generator to the consumer Analyse the make of the emergence of AC and DC generators on companionship and the environsEven good electrical conductors like blur used to supply electricity, sometimes through considerable cable lengths to towns and cities, generate warm resistances. It follows that to minimise energy loss in the wires, the current needs to be unploughed low ( high temperature losses vary as the square of the current). This is achieved by transmitting the energy at high voltages. Impact on society Impact on environment Positive Improved lifestyle pass age lighting Electric trains Communication Computerisation of galore(postnominal) systems eg. anking, stock market Industrial development a more jobs Lots of electric trains have precipitated pollution from go trains and made public transport more available Electricity has replaced older, more-polluting technologies eg. electrical heating instead of combust burning in fireplaces Negative Possible risk of crabmeat living near statistical distribution cables longish working hours Reliance on electricity leaves us vulnerable to systems loss due to electrical failure Burning coal in motive displace produces dummy and CO2 (a greenhouse gas) Nuclear force play stations produce radioactive water & have a risk of nuclear accident Hydroelectric schemes redirect water away from river habitats Mining impacts negatively on environment Visual pollution of cables treasure evidence about the physiological effects on humans living near high voltage government agency lines 1979 pic k up found children living near high voltage power lines appeared to develop a particular form of cancer. 997 study showed no evidence of an increase risk of childhood cancer at residential magnetic field levels. 1998 panel stated that EM field should be considered possible human carcinogens and that there is no conclusive and consistent evidence that EM fields cause any human disease. William Kim HSC Physics Summary page 28 4. Transformers allow generated voltage to be either increased or decreased before it is used Explain the purpose and principles of transformers in electrical circuits A transformer is a device that alters the voltage and current of an electricity supply.The AC voltage source produces an alternating current in the uncreated coil. This produces an alternating B field that wander through the collateral coil. The petty(a) coil now has Conductor B field Change and therefore generates its own voltage. If there is a closed loop then an alternating current w ill flow as well. Compare step-up and stepdown transformers come to the fore transformers increase voltage and decrease current Step-down transformers decrease voltage and increase current Determine the relationship between the ratio of the number of turns in the immemorial and unoriginal coils and the ratio of primary to secondary voltage Vp = primary voltage (voltage in) Ip = primary current np = number of turns on primary coil Vs = secondary voltage (voltage out) Is = secondary current ns = number of turns on secondary coil Vp Vs = np ns If 100% efficient (this needs perfect flux linkage, usually using an iron core) then situation in primary = Power in secondary ? V p I p = Vs I s ? ? Vp Vs Vp Vs = = Is Ip np ns = Is IpWilliam Kim HSC Physics Summary page 29 Explain why voltage transformations are related to the conservation of energy The dominion of Conservation of Energy states that energy cannot be created or destroyed but that it can be transformed from one form to an other. This means that if a step-up transformer gives a greater voltage at the output, its current must be decreased i. e. power in = power out. Explain the role of transformers in electricity sub-stations NSW power stations produce electricity with a voltage of about 23,000 V and a current of about 30,000 A.Unfortunately, this amount is too high to be sent through a cable. This is because it heats the cable causing energy loss. This is called joule heating and happens because P = I2R So to reduce joule heating, the current must be reduced as much as possible with a step-up transformer. redundant transformers between the power station and consumer (in sub-stations) bit by bit stepdown the voltage, to 240 V by the time it gets to kinsfolk users. This is because at high voltages, electricity can conduct through air, making it grave for use in the stead. Discuss why some electrical appliances in the dwelling that are committed to the mains municipal power supply use a transform er approximately electronic circuits are designed to function at low DC voltages of between 3 V and 12 V. Therefore, home appliances that have electronic circuits in them will have either a plug-in transformer or an inbuilt transformer to step down the domestic 240 V supply. These transformers also have a rectifier circuit built into them that converts AC to DC.TVs also contain a step-up transformer for producing the high voltages needed for the CRT. Analyse the impact of the development of transformers on society The development of the generator and transformer has allowed for the setting up of national power grids in almost every country, making that most convenient and flexible form of energy, electricity, accessible from many miles away. The transformers role is to step voltage up and down to make efficient transportation and distribution possible. William Kim HSC Physics Summary page 30 5.Motors are used in industries and the home usually to convert electrical energy into more useful forms of energy Describe the main features of an AC electric motor AC generality motor The rotor end rings short circuit non-ferrous rotor bars, that is sealed i. e. no external connections at all (usually a squirrel detain). Encased in a laminated iron armature. The stator ring electromagnet. Connection to stator the surrounding electromagnet receives the AC. In an AC conclusion motor, the principle of operation is 1. AC to surrounding electromagnet, which 2.Produces an oscillating (rotating) B field, which 3. Induces a current in the rotor, which 4. Turns the rotor into an electromagnet that 5. Tries to oppose the field being generated by the stator. 6. The stator and the rotor push against each other (using their B fields), which 7. Causes the rotor to turn Brilliant AC (synchronous) motor A rotating coil Surrounding magnets Connection to coil via slip rings (commutator for DC motor) Explain that AC motors usually produce low power and relate this to th eir use in power tools Power is the rate of work. Work is done when energy is transformed from one type to another.Induction motors are considered to produce low power because the amount of mechanical work they achieve is low compared with the electrical energy consumed. The lost power of induction motors is consumed in magnetising the working move of the motor and in creating induction currents in the rotor. AC induction motors are considered to be unsuitable for use in heavy industry because their low power rating would make them too expensive to run when performing a specific task. However, they are used extensively in power tools and electric domestic appliances where the loss of power is not economically significant. Explain the advantages of induction motors Advantages of AC induction motors 1. Simplicity of design 2. High efficiency (hence low keep there are no brushes or commutators to wear out) 3. Relatively low woo William Kim HSC Physics Summary page 31 Core Topic Th ree From Ideas to Implementation 1. Increased understandings of cathode rays led to the development of telly Explain that cathode ray tubes allowed the manipulation of a stream of charged particles Discharge Tubes investigation of vacuum tubes could not occur until good vacuum sums had been invented.A vacuum tube is a churl tube fitted with an electrode at either end, and almost all of the air sucked out. The positive electrode is the anode The negative electrode is the cathode. When a high voltage is connected between the electrodes, an in microscopic ray travels from the cathode to the anode. They were called cathode rays. Cathode rays cause glass to glow green. A discharge tube is a cathode ray tube with a vacuum pump fitted, so that the air pressure interior the tube can be varied. At different air pressures, different bright effects appear in the tubes e. . bands, striations and dismal spaces. These are caused by cathode rays striking atoms in the air inside the tube. The atoms become activated then release photons of visible light A beam of electrons travels from the cathode to the anode and can be deflected by electrical and/or magnetic fields. Anode Glass glows here Cathode Explain why the apparent inconsistent behaviour of cathode rays caused dig as to whether they were charged particles or electromagnetic waves In 1892 cycle per second demonstrated that cathode rays could permeate thin metal foils.This he believed support a wave nature. In 1895 Jean-Baptise Perrin showed that cathode rays deposited negative charges on impact with an object, suggesting a particle nature. There was controversy over the nature of cathode rays waves or particles. William Kim HSC Physics Summary page 32 Identify that charged plates produce an electric field If metal plates are separated by a distance and are attached to a power source, an electric field will be produced between them. E = V/d Describe quantitatively the force acting on a charge moving th rough a magnetic fieldRecall that the force (F) acting on a charge (q) moving with a velocity (v) at an angle to a magnetic field (B), is given by FB = qvB Where FB = magnetic force (N) q = charge (C) v = velocity of charge (ms-1) B = magnetic field strength (T) Discuss qualitatively the electric field strength due to a point charge, positive and negative charges and oppositely charged parallel plates. Describe quantitatively the electric field due to oppositely charged parallel plates ++++++++ If a positive charge is placed near another positive charge, it will experience a force of repulsion.A positive charge placed in a field will experience a force in the direction of the arrow. A negative charge placed in a field will experience a force opposite to the direction of the arrow. FE = qE Where FE = electric force (N) q = charge (C) E = electric field strength (NC-1) William Kim HSC Physics Summary page 33 Outline Thomsons experiment to measure the charge/mass ratio of an elect ron Cathode ray particles ? v? B ? ? ? ? ? ? ? FM ? ? FE ? ? ? v? E ? ? ? J. J. Thomsons Experiment By fitting plates to his CRT, he could subject the cathode rays to an electric field.The rays deflected, proving that they were charged particles, not electromagnetic waves. He noticed that the rays deflected toward the positive plate, proving that they were negatively charged particles. By crossing electric and magnetic fields, Thomson was able to deduce the velocity of the cathode rays. By turning off the E field, the particles followed a circular arc caused by the B field. The magnetic force was acting like a centripetal force. mv qvB = r q v ? = m Br 2 ? FM = FE qvB = qE E ? v = B Thomson adjusted the strength of the fields so that the particles were not deflected.By carefully bar the strength of the fields, Thomson could calculate v. Thomson had already measured B and worked out v. By beat the radius of curvature r, he could then calculate q/m, i. e. the charge/mass ratio o f an electron. q/m for these particles was 1800 times greater than for a heat content ion, the simplest known atomic ion. Thomson pronto compared the charges and found them to be about the same (though opposite in sign) Therefore mass for cathode ray particles was 1800 times smaller than hydrogen Therefore cathode ray particles were subatomic particlesThis was the first of all discovery of subatomic particles They were later called electrons. William Kim HSC Physics Summary page 34 Outline the role in a cathode ray tube of Electrodes in the electrode gun The electric field The fluorescent screen The Cathode jibe Tube Each CRT has a vacuum tube/chamber, a cathode, an anode, and a target. Electrodes in the electron gun The electron gun produces a narrow beam of electrons. It consists of a filament, a cathode and two open-cylinder anodes. The anodes help to accelerate and focus the electrons.A ring shaped electrode the grid between the cathode and anodes controls the brightness level of the spot by controlling the number of electrons emitted by the gun. By making the grid negative with respect to the cathode the number of electrons, and hence the brightness is reduced. The electric field Acts as a deflection system. It consists of two sets of parallel plates connected to a parallel plates connected to a potential difference. This produces an electric field between the plates. The Y-plates control the vertical deflection and the X-plates the horizontal deflection.The fluorescent screen The inside glass of the end of the tube is coated with a fluorescent material for example, zinc sulphide. When an electron beam hits the screen, the coating fluoresces and a spot of light is seen on the screen. The screen acts as a detector of cathode rays. Electrons Cathode Anode To plates and screen William Kim HSC Physics Summary page 35 Outline applications of cathode rays in oscilloscopes, electron microscopes and television sets The Cathode Ray Oscilloscope (CRO) Is an electronics diagnostics device because it can show a graph of how voltages vary over time.Deflection of the electron beam is achieved by two sets of plates. Horizontal plates cause vertical deflection while vertical plates cause horizontal deflection. TV Tube An electron gun again produces the electron beam. Coils are used instead of plates, however. Electric current through the coils produce magnetic fields that can deflect the beams quickly from side to side, and more slowly from bottom to top. In this way the beam scans the entire screen. By varying the intensity of the beam, a visualise is built up. The picture is refreshed 50 times / second, which is too fast to be noticed by the human eye.The Electron Microscope Uses electrons instead of light. Their wavelength is 100,000 times smaller than visible light, therefore their resolving power is 100,000 times greater. A sample is placed inside the chamber (which is really the CRT) The air is then sucked out An electron gun pr oduces the electron beam Coils produce magnetic fields to focus the beam (magnetic lenses) The beam scans over the surface of the sample Detectors pick up the reflected and scattered electron beam, and from this information a 3 dimensional estimate is constructed Discuss the impact of increased understandings of cathode rays and the development of the oscilloscope on observational physics The introduction of electronic control systems into all forms of science and industry has seen the cathode ray oscilloscope (CRO) become one of the most wide utilised test instruments. Because of its ability to make voltages visible, the cathode ray oscilloscope is a fibrous diagnostic and development tool. William Kim HSC Physics Summary page 36 2.The reconceptualisation of the model of light led to an understanding of the photoelectrical effect and black body radiation Explain qualitatively Hertzs experiments in measuring stick the speed of radio waves and how they relate to light waves Recall Maxwells theory of electromagnetic waves In 1864 Maxwell, through a set of four resplendent equations, predicted a range of invisible waves made up of an electric and magnetic wave that regenerate each other. The speed of these waves was mensural to be 3 x 108 ms-1 and belike include light.E v B Heinrich Hertzs Experiment (proving Maxwells theory) Performed in 1886, Hertz built equipment to generate and transmit EM waves with ? ? 1m. He also had a separate receiving system (a loop of wire) located about 20m away. Spark gaps were included to show when high voltage AC was present in the vector or receiver. The receiver bow only appeared when the transmitter spark was present. Hertz hypothesised that the sparks set up changing electric and magnetic fields that propagated as an electromagnetic ave, as postulated by Maxwell. He showed that these were waves being transmitted because he could reflect, refract and polarise them. By measuring the frequency, he calculated v (v = f ? ) and it came out as 3 x 108 ms-1. These properties proved Maxwells theory and as they are also exhibited by light, Hertz was able to provide experimental evidence that light is a form of transverse electromagnetic wave. to induction coil 1mm gap transmitter charged plates receiver William Kim HSC Physics Summary page 37 Describe Hertzs observation of the effect of a radio wave on a receiver and the photoelectric effect he produced but failed to suss out Outline applications of the production of electromagnetic waves by oscillating electric charges in radio antennae Hertz observed that the transmitter spark was producing s