Upcoming SlideShare
×

All phy note for O lvl

5,070

Published on

Published in: Technology, Health & Medicine
6 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total Views
5,070
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
443
0
Likes
6
Embeds 0
No embeds

No notes for slide

Transcript of "All phy note for O lvl"

1. 1. 1 | P h y s i cTheme1 General PhysicsMeasure Instrument- Vernier calipers + micrometer screw gaugePendulum – one oscillation√***even in a vacuum, T of different l is not the sameSpeed: the distance moved per unit timeVelocity: the change in displacement per unit timeDisplacement: distance in a specific directionAcceleration: the change in velocity with timeAddition formula( )Air resistance: a frictional force1. Apply on only moving objects2. Air resistance↑ when Speed↑ surface area↑ density of air↑Force: a push or pull that one object exerts on anotherScalar: only magnitude
2. 2. 2 | P h y s i cVector: direction + magnitude***For an object with constant velocity or zero acceleration, theresultant force/net force is zeroNewton’s 1stlaw‚Every object will continue in its state of rest or uniform motion in astraight line unless a resultant force acts on it to change its state‛Newton’s 2ndlaw‚When a resultant force acts on an object of constant mass, the objectwill accelerate and move in the direction of the resultant force. Theproduct of the mass and acceleration of the object is equal to theresultant force.‛Newton’s 3rdlaw‚For every action, there is an equal and opposite reaction, and theseforces act on mutually opposite bodies.‛Mass: a measure of the amount of matter or substance in a bodyWeight: a force due to gravityGravitational field: the region surrounding the Earth where gravity isexperiencedGravitational field strength: the gravitational force acting per unitmass on an objectInertia: the reluctance of the object to change its state of rest ormotion***Inertia depends on only the mass of the objectDensity: mass per unit volume
3. 3. 3 | P h y s i cMoment: the product of the force and the perpendicular distance from thepivot to the line of action of the force***Taking moments to the pivot, sum of anti-clockwise moment = sum ofclockwise momentPrinciple of Moments‚When a body is in equilibrium, the sum of clockwise moment about apivot is equal to the sum of anti-clockwise moment of the same pivot‛Centre of Gravity: the point through which its whole weight appears toact for any orientation of the object*** A plumb line is used to find CGStability: the ability of an object to return to its original objectafter it has been tiled slightlyStable, Unstable and Neutral equilibrium (CG remains at the same levelwhen it is tiled slightly)***Low CG and wide base to increase stabilityEnergy: the capacity to do workKinetic Energy: the energy possessed by a body due to its virtual ofmotionGravitational Potential Energy: the energy possessed by a body due tovirtual of its positionPrinciple of Conservation of Energy‚Energy can neither be created nor destroyed in any process. It can beconverted from one form to another or transferred from one body toanother, but the total amount remains constant‛
4. 4. 4 | P h y s i cWork: the product of the force and the distance moved by the object inthe direction of the force(1J=1Nm)Power: the rate of woke done(1W=1J/s)Pressure: the force acting per unit area,*** Barometer is used to measure the atmospheric pressureTheme2 Thermal PhysicsTemperature: how hot or cold an object isHeat: the amount of energy that is being transferred from a hotter to acolder regionThermocouple – electromotive force ( )Factors affecting range, sensitivity and responsiveness
5. 5. 5 | P h y s i cState Arrangement MovementsClosely packed in a regularpatternVibrate about their fixedpositionlClosely packed in a disorderlymannerSliding over each othergspread far apart in a disorderlymannerMove rapidly at randomBrownian motion: the random, continuous and uneven movement of particlessuspended in a fluidBoyle’s Law: pressure is inversely related to volume when the otherfactors are constantOverall formulaKey conceptsWhen the container is heated up (temperature increases); the particlesgain more kinetic energy and move faster randomly, the rate of collisionbetween the particles and the inner wall is more frequent, the totalforce exerted to the inner wall increases, the pressure increasesWhen the volume is decreased; the space between the particles issmaller, the number of molecules presented per unit volume increases,the rate of collision between the particles and the inner wallincreases, the total force exerted to the inner wall increases, thepressure increases
6. 6. 6 | P h y s i cConduction: the process of thermal energy transfer without any flow ofthe material medium- Particle vibration; metal and non-metal- Free electron diffusion; only metalConvection: the transfer of thermal energy by mean of currents in afluidRadiation: the continual emission of infrared waves from the surface ofall bodies, transmitted without the aid of a medium***Dull, black surfaces are better emitters of infrared radiation thanshiny, white surfacesInternal energy: The total kinetic and potential energy associated withthe motions and relative positions of the molecules of an objectHeat capacity(C): the amount of thermal energy required to raise thetemperature of a body by 1K (or 1˚C)Specific heat capacity(c): the amount of thermal energy required toraise the temperature of 1kg of a substance by 1K (or 1˚C)Melting: the process of the change of solid state to liquid stateP b.p.***increase pressure increase the melting point of waterLatent heat: the energy released or absorbed during a change of stateLatent heat of fusion: the amount of thermal energy required to change abody from solid to liquid state, or vice versa, without a change intemperatureSpecific latent heat of fusion: the amount of thermal energy required tochange 1 kg of solid to liquid, or vice versa, without a change intemperature
7. 7. 7 | P h y s i cLatent heat of vaporisation: the amount of thermal energy required tochange a body from liquid to vapour, or vice versa, without a change intemperatureSpecific latent heat of vaporisation: the amount of thermal energyrequired to change 1 kg of liquid to vapour state, or vice versa,without a change in temperature,Boiling: the process of the change of liquid state to gaseous state at afixed and constant temperatureBoiling Evaporation1. Occurs at a fixed temperature 1. Occurs at any temperature2. Quick process 2. Slow process3. Takes place throughout theliquid3. Takes place only at the liquidsurface4. Bubbles are formed in the liquid4. No bubbles are formed in theliquid5. Thermal energy supplied by anenergy source5. Thermal energy supplied by thesurroundingsTheme3 Light, Waves and SoundLuminous and non-luminous objectNumber of imaged formed – always round downRefraction: Bending effect of light as it passes from one opticalmaterial to anotherRefractive index – Snell’s Law
8. 8. 8 | P h y s i c***light travels from lesser density to higher densityCritical angle: the angle of incidence in the optically denser mediumfor which the angle of refraction in the less dense medium is 90°Total internal reflection takes place only when1. A ray of light travels from an optically denser to a less densemedium2. The angle of incidence in the optically denser medium is greater thanthe critical angleOptical fibres_ can carry a much higher volume of information over long distances thanthe electrical wires_ lighter, thinner and cheaper for manufacture_ high quality transmission of information over long distances withnegligible lossLaws of Reflection11. Angle of incidence is equal to the angle of reflection2. The incident ray, reflected ray and the normal at the point ofincidence all lie on the same planeLensPeriodic motion: motion repeated at regular intervals***the source of any wave is a vibration or oscillation***waves move/propagate through the medium***In waves, energy is transferred without the medium being transferred
9. 9. 9 | P h y s i cTypes of wave motion1. Longitudinal waves: waves that travel in a direction parallel to thedirection of the vibration2. Transverse waves: waves that travel in a direction perpendicular tothe direction of the vibrationCrests: the highest points of a transverse waveTroughs: the lowest points of a transverse wave***Compressions & rarefactions in longitudinal wavesPhase: any two points that move in the same direction, have the samespeed and same displacement from the rest positionWavelength (λ): the shortest between two points that are in phaseAmplitude (A): the maximum displacement from the restPeriod (T): the time taken for one point on the wave to complete oneoscillationFrequency (ƒ): the number of complete waves produced per secondƒWave speed (v)
10. 10. 10 | P h y s i cλƒλWave front: an imaginary line on a wave that joins all points that arein the same phaseRefraction of waves*** v & λ decrease from deep to shallow waterReflection of waves- i = r- f, λ, v are the sameElectromagnetic waves – low f, high λ to high f, low λ; Radio waves  microwaves  infrared  visible light*  ultraviolet X-rays  gamma rays***red  blueProperties of Electromagnetic waves1. They are transverse waves. They are electric (horizontal) andmagnetic (vertical) fields that oscillate at 90 to each other2. They transfer energy from one place to another
11. 11. 11 | P h y s i c3. They can travel through vacuum, do not require any medium4. Their speed in vacuum is 3.0108m/s25. ƒλ6. They obey the laws of reflection and refraction7. They carry no electric charge8. Their ƒ do not change when travel from one medium to another. Their ƒdepend only on the source of the wave. Their v and λ change.Ionisation: the process of ion formationIonising radiation: the rejection of one or more electrons from an atomor molecule to produce a fragment with a net positive chargeEffects of ionising radiation1. Molecular level: irradiation of human tissues, damage to proteins,nucleic acid2. Sub-cellular level: damage Chromosomes (DNA)3. A pregnant woman: an abnormal pattern of cell division, leading tocancers such as leukaemia4. Organism level: premature aging and shortening of lifespan***Sound is longitudinal wave***Sound is produced by vibrating sources placed in a medium***the series of compressions and rarefactions produced by the shiftingof air layersCompressions – slightly higher pressure than the surrounding airpressureRarefactions – slightly lower pressure than the surrounding airpressure
12. 12. 12 | P h y s i cWavelength of the sound (λ): the distance between two consecutivecompressions or rarefactionsAmplitude of the sound (A): the maximum pressure changeMedium of transmission of soundV gas  5 =V liquidV gas  15 =V solidV solid > V liquid > V gas√ , T=temperatureReflection of soundEcho: the repetition of the clap***an echo is formed when a sound is reflected off hard, flat surfacesRange of audibility: the range of frequencies which a person can hear***human ears – 20 Hz-20,000 HzUltrasound: sound with frequencies above the upper limit of the humanrange of audibility (above 20,000 Hz)Infrasound: sound with frequencies below the lower limit of the humanrange of audibility (above 20 Hz)Pitch – a music note or sound as ‘high’ or ‘low’ƒLoudness: the volume of a sound related to the amplitude of a soundTheme4 Electricity and Magnetism
13. 13. 13 | P h y s i cElectrostatics: the study of static electric charges***same charges – repel (repulsive force)***different charges – attract (attractive force)The amount of charge an e-/P+has is 1.610-19C6.2510-19electrons = 1 CElectrical insulators: materials where electrons are not free to moveabout***they are charged by frictionElectrical conductors: materials that allow electrons to move freelywithin them***they are charged by inductionInduction: the process of charging a conductor without any contact withthe charging bodyInduction – 2 metals1. Two conductors (metal spheres) on insulating stands are placedtouching each other2. A negative charged rod is brought near sphere A. This causes theelectrons in the metal spheres to be replied to the far end of sphere B.Sphere A can be seen to have excess positive charges, while sphere B hasexcess positive charges.3. Without removing the rod, separate spheres A and B.4. Remove the charged rod. Spheres A and B now have equal amounts ofopposite charges. Spheres A and B have been charged by induction.Induction – 1 metal
14. 14. 14 | P h y s i c1. Bring a positively charged glass rod near the metal conductor on aninsulating stand. The free electrons in the metal will be drawn towardsthe side nearer the positively charged glass rod.2. Without removing the glass rod, earth the positively charged side ofthe metal conductor by touching in with your hand. The human body is arelatively good conductor and will allow electrons to flow into theconductor from the ground. This will neutralize the positive on thisside of the conductor.3. With the glass rod still in place, remove your hand from theconductor. This will stop the earthing process.4. Remove the glass rod. The negative charges will be redistributed onthe surface of the conductor. The conductor is now negatively charged.Electric force: a force experienced by chargesAn electric field: a region where an electric charge experiences anelectric forceElectric lines of force: imaginary lines, showing the path a positivecharge would take if it was free to move.The direction of the field: the direction of the force on a smallpositive charge***The strength of an electric field is indicated by how close the filedlines are to each other
15. 15. 15 | P h y s i cAn electric current is caused by a flow of electronsElectron flow: movement of electrons from the negatively charged end tothe positively charged endConvectional current flow: the assumption that an electric currentconsist of positive charges flowing from the positively charged end tothe negatively charged endAn electric current (I): a measure of the rate of flow of electriccharge (Q) through a given cross section of a conductorAn electric circuit: a complete or close path through which charge canflow from one terminal of an electrical source to the other terminalThe electromotive force (e.m.f.) of an electrical energy source: thework done by the source in driving a unit charge round a completecircuitCells in series‚The combined e.m.f. in increased because electric charges gainelectrical energy from each cell when they pass through them.‛Cells in parallel
16. 16. 16 | P h y s i c‚The energy required to move electric charges through the load will becontributed equally by each cell. Thus, each cell only needs to providehalf the energy to move the charges through the circuit.‛Potential difference (p.d.) between two points in an electric circuit:the amount of electrical energy converted to other forms of energy whenone coulomb of positive charge passes between the two pointsResistance: a property of the material that restricts the movement offree electrons in the materialThe resistance (R) of a component: the ratio of the potential difference(V) across it to the current (I) flowing through itA resistor: a conductor in a circuit that has a known value ofresistanceOhm’s Law‚The current passing through a metallic conductor is directlyproportional to the potential difference across its ends, provided thephysical conditions are constant‛***ohmic conductors – conductors that obey Ohm’s Law*** I-V graph: a straight line passes through the originNon-ohmic conductors – I-V graph is not a straight line ( is not aconstant)Ex; Filament lamp, thermistor, semiconductor diode
17. 17. 17 | P h y s i cResistivity (ρ)Series Circuits‚When similar resistors are connected in series, the combinedresistance is larger than the individual resistance of a singleresistor. As a result, this cause the current in the circuit to besmaller if the e.m.f. supplied in the same.‛‚In a series circuit, the sum of the potential across each component isequal to the difference across the whole circuit‛‚The combined resistance of resistors in series is the sum of all theresistances.‛Parallel Circuits
18. 18. 18 | P h y s i c‚In a parallel circuit, the sum of the individual currents in each ofthe parallel branches is equal to the main current flowing into and outof the parallel branches.‛***Bulbs connected in parallel will glow more brightly than whenconnected in series***Another advantage of connecting bulbs in parallel is that when one ofthe light bulbs blows, the other light bulb will continue to glow –there is still a complete circuit through the other parallel branch forthe current to flow≠***When one of the bulbs in series blows, the entire circuit will beopen and the other bulb will not light upPotential Divider: A circuit with resistors arranged in series( )
19. 19. 19 | P h y s i cTransducers: electric or electronic devices that convert energy from oneform to another – they respond to physical quantities such astemperature and lightInput transducers – convert non-electrical energy to electrical energyOutput transducers – convert electrical energy to non-electrical energyEx; Thermistors, Light-dependent resistor (LDR)Thermistors –Light-dependent resistor (LDR) –Electric heating_ Usually made up of nichrome wire; because of its high resistivity andability to withstand high temperature;_ As it has high resistivity, the electric current is decreased andhence the temperature cannot reach the m.p. and b.p._ Thermal energy is generated when an electric current passes throughthe heating element
20. 20. 20 | P h y s i cElectric lighting – filament & fluorescent lampFilament lamp_ Filament is made of a tungsten coil; tungsten has high resistivity andm.p. (3400°C)_ Filament is thin (small cross-sectional area – A)***↑ρ ↑l ↓A  ↑R  ↓I  temperature cannot reach the m.p._ contains Argon and Nitrogen to prevent the tungsten to burntFluorescent lamp_ more efficient than filament lamps (3000 hours vs 1000 hours)_ use less energy than filament lamps_ light produced when passing electric charges between two electrodes_the mercury vapour contained in the glass tube emits ultraviolet lightwith invisible light which is converted to visible light by fluorescentpowder coated on the inner wallAdvantages DisadvantagesFilamentGive cosy and relaxedatmoshere10%  light90%  heatFluorescent Energy efficient Costly & toxicElectric motors_ work on the principles of the magnetic effects of a current_ electric energy  rotational kinetic energyPower: the rate of woke done or energy convertedDangers of ElectricityDamage insulation_ electrical insulation crack and break; exposing the conducting wiresinside_ cause severe electric shock if it is touchedOverheating of cables_ an unusually large current flows through the conducting wires
21. 21. 21 | P h y s i c_ the higher resistance of thinner wires will produce more thermal heatthat will damage the insulation and may cause a fire***thin wires are used for appliances that need less power and viceversaDamp conditions_ as our human body can only withstand a current of about 50mA, thelarge current will electrocute the person_ R of human body is low; ↓R  ↑I ***Safe use of electricity at home_ electricity is supplied by a cable containing 2 wires – live wire (L)and neutral wire (N)live wire (L) – 240Vneutral wire (N) – 0VThese 2 wires are connected to a main fuse box, an electricity meter anda consumer unit.The consumer unit: the distribution point for the household’selectricity supply. – consists of a main switch and circuit breakers1. Circuit breakers: safety devices that can switch off the electricalsupply in a circuit when there is an overflow of current1.1 Miniature Circuit Breaker (MCB): when the current exceeds thecurrent values labeled, the circuit breaker will trip.1.2 Earth Leakage Circuit Breaker (ELCB): detects the small currentleakages from the live wire to the earth wire. When this happens, thecurrent in the live wire will be greater than the neutral wire, causingthe ELCB to trip.2. Fuses: safety devices included in an electrical circuit to preventexcessive current flow_ same function as the MCB
22. 22. 22 | P h y s i c_ A fuse consists of a short thin piece of wire which becomes hot andmelts when the current flowing through it is greater than its ratedvalue.a. Fuses should have a current rating just slightly higher than thecurrent an electrical appliance will use under normalb. A fuse should be connected to the live wire so that the appliancewill not become charged after the fuse has melted due to the over flowof currentc. Before you charge a fuse, always switch off the mains power supply3. Switches_ they break or complete an electrical circuit‚If the switch id fitted onto the neutral wire, the appliance will be‘live’ even though the switch is ‘off’. Anybody who touches themetal casing the appliance would experience an electric shock.‛ –wrong_ Switches must be fitted onto the live wire so that switching off disconnects the high voltage from an appliance – correct4. Plugs and sockets_ a cartridge fuse protects the appliance from excessive current flow5. Earthing_ earth wire (E) – green & yellow_ live wire (L) – brown_ neutral wire (N) – blue
23. 23. 23 | P h y s i cThe earth wire: a low-resistance wire which usually connected to themetal casing of the appliance‚If there is a fault – the live wire touches the metal casing of theappliance – the user could get an electric shock.‛_ the earth wire connected to the metal casing diverts the large currentdue to the electrical fault to the ground6. Double insulation_ a safety feature which provides 2 levels of insulation in anelectrical appliance that can substitute the earth wire6.1. The electric cable is insulated from the internal components of theappliance6.2. The internal components are also insulated from the external casingMagnetite: a naturally occurring iron oxide mineralMagnetic/ferromagnetic materials: the materials that are attracted by anatural magnetA permanent magnet: a material that retains its magnetism for a longtimeProperties of magnets1. The poles are where the magnetic effects are the strongest.2. When we suspend a bar magnet freely, the north-seeking pole willpoint to the North Pole and the south-seeking pole will point to theSouth Pole.3. Law of magnetism‚Like poles repel, unlike poles attract‛Repulsion: the only test to confirm that an object is a magnetMagnetic Induction: the process where ferromagnetic materials becomemagnetised when they are near or in contact with a permanent magnet
24. 24. 24 | P h y s i cTheory of magnetism‚If we take a bar magnet and cut it into three smaller pieces, we willnotice that every piece becomes a magnet itself with an N pole and an Sploe.‛A magnetic domain: a group of atomic magnets pointing in the samedirection***In a permanent bar – the magnetic domains point in the samedirection***In an unmagnetised bar – the magnetic domains point in randomdirection; the magnetic effects of the atomic magnets cancel out sothere is no resultant magnetic effectPhenomena1. Magnetic saturation‚Every magnet has a maximum strength when all the magnetic domains arepointing in the same direction‛ – the magnet is magnetically saturated2. Demagnetisation of magnetsDemagnetisation: the process of removing magnetism from a magnetEx; heating, hammering‚They cause the atoms of the magnet to vibrate vigorously, mixing upthe directions of the magnetic domains.‛3. Storage of magnets using soft iron keepers
25. 25. 25 | P h y s i c‚If we store magnets side by side, the magnets become weaker after sometime as ‘free’ poles near the ends of the magnet will repel oneanother. The magnetic domains will be altered, weakening the magnets.‛‚We store bar magnets in pairs by using soft iron keepers across theends of the bar magnets. The poles of the atomic magnets are in closedloops with on ‘free’ poles to weaken the magnetic domains.‛Ways of making magnets1. Stroking method***precaution is that the stroking magnet must br lifted sufficientlyhigh above the steel bar between successive stroke.2. Electrical method using a direct current‚When an electric current flows through the solenoid, it produces astrong magnetic field which magnetizes the steel bar.‛***The poles of the magnet is determined by the right-hand grip ruleWays to demagnetising magnets1. Heating‚The atoms of the magnet vibrate vigorously when heated, causing themagnetic domains to lose their alignment.‛2. Hammering
26. 26. 26 | P h y s i c‚Hammering alters the alignment of the magnetic domains, causing themagnet to lose its magnetism.‛3. Electrical method using an alternating current‚An alternating current is an electric current which varies itsdirection many times per second. The magnet is then slowly withdrawn inthe East-West direction with the alternating current still flowing inthe solenoid.‛A magnetic field: a region in which a magnetic object, placed within theinfluence of the field, experiences a magnetic forceMagnetic field lines: invisible lines of force which we assume areemerging from the North Pole and entering the South pole of the magnet_ Magnetic field lines do not cross or intersect one another_ the field lines drawn closer together represent strong magnetic fields_ the field lines drawn further apart together represent weak magneticfields***the point between two N poles is the neutral pointThe earth’s magnetic fieldA large imaginary magnet within the earth is believed to be caused byconvection currents inside the earth’s molten outer coreThe imaginary ‘S’ pole is at the geographic north poleThe imaginary ‘N’ pole is at the geographic south poleMagnetic shielding: a method of creating a region or space that is freeof magnetic fields by means of a closed loop of soft magnetic materials_ use thin sheets of soft magnetic materials; they work by diverting themagnetic fields
27. 27. 27 | P h y s i c‚Magnetic field lines tend to pass through magnetic materials easily.‛Iron –soft magnetic material_ gain and lose magnetism easily; strong induced magnet_ induced magnetism occurs instantaneously either induced by anothermagnet, or by a solenoid conducting electricity_ loses its induced magnetism when the inducing magnet is removed_ a temporary magnet; does not retain its magnetismSteel –hard magnetic material_ difficult to gain and lose magnetism; weak induced magnet_ induced magnetism occurs slowly_ does not lose its induced magnetism easily once steel is magnetised_ a permanent magnet; retain its magnetism‚A current-carrying conductor produces a magnetic field around it.‛***using right-hand grip rule to find the direction of the magneticfield around the wire***the magnetic field of a long, straight current-carrying wire isstronger when it is closer to the wire or when a large current flowsthrough the wire
28. 28. 28 | P h y s i cTo increase the magnetic field strength at the centre of the flat coil1. increase the current2. increase the number of turns of the coilTo increase the magnetic field strength in a solenoid1. increase the current2. increase the number of turns per unit length of the solenoid3. place a soft iron core within the solenoid; the soft iron coreconcentrates the magnetic field lines, thereby increasing the magneticfield strengthUses of electromagnetsCircuit breaker
29. 29. 29 | P h y s i c_ When the current in a circuit increases, the strength of theelectromagnet will increase in accordance; this will pull the soft ironarmature towards the electromagnet._ As a result, the spring pulls apart the contact and disconnects thecircuit immediately, and the current stop to flow._ We can reconnect the circuit by using the reset button. The resetbutton can be pushed to bring the contact back to its original positionto reconnect the circuit.Motor effect‚The force on the current-carrying conductor in a magnet field actsperpendicular to both the direction of the current and the direction ofthe magnetic field.‛‚The force is reversed when we reverse the direction of the current ormagnetic field.‛Fleming’s Left-Hand Rule_ Thumb – motion_ Forefinger – field_ Second finger – currentCombined magnetic field when the wire is placed between the poles of themagnet
30. 30. 30 | P h y s i c_ the combined field lines acting in the same direction gives a strongerfield than the combined field lines acting in the different direction forceForces between two parallel current-carrying wires‚Currents in opposing directions cause repulsion. Currents in similardirections cause attraction.‛To increase the turning effect on the wire coil in a magnetic field1. increase the number of turns on the wire coil2. increase the current in the coil – lower the resistance / increasethe voltage supply3. insert a soft iron core into the coil to concentrate the magneticfield lines4. use stronger permanent magnetThe D.C. motor_ electrical energy  mechanical energy
31. 31. 31 | P h y s i cComponents1. Rectangular coil connected in series to a battery and rheostat2. Permanent magnets3. Split-ring commutator4. two carbon brushesSplit-ring commutator; to reverse the direction of the current in the loop (coil every half arevolution) whenever the commutator changes contact from one brush tothe otherCarbon brushes; to conduct current to flow into and out of the coilElectromagnetic induction: the phenomenon of inducing on electromotiveforce (e.m.f.) in a circuit due to a changing magnetic fieldThe magnitude of this induced e.m.f. depends on;1. the number of turns in the solenoid2. the strength of the magnet3. the speed inserting the magnet or withdrawing from the solenoidFaraday’s law of electromagnetic induction‚The e.m.f. induced in a conductor is proportional to the rate ofchange of magnetic lines of force linking the circuit.‛
32. 32. 32 | P h y s i cLenz’s law‚The direction of the induced e.m.f., and hence the induced current ina circuit, is always such that its magnetic effect opposes the motion orchange producing it.‛***There is no e.m.f. generated when bar magnet is stationaryAn A.C. generator: a device that uses the principle of electromagneticinduction to transform mechanical energy into electrical energyAlternation current generators (A.C. current)_ the slip rings ensures that the direction of the induced currentflowing in the external circuit changes every half revolution‚The induced e.m.f. is maximum when the coil in parallel to themagnetic lines of force. The coil experiences the greastest changes inmagnetic field.‛
33. 33. 33 | P h y s i c‚The induced e.m.f. is zero when the coil in perpendicular to themagnetic lines of force as the coil is not cutting through the magneticfield lines. The coil experiences no changes in magnetic field.‛To increase the induced e.m.f.1. increase the numbers of turns on the coil2. increase the frequency of rotation of the coil3. use stronger permanent magnets4. insert a soft iron core into the coil to concentrate the magneticfield linesThe fixed coil A.C. generator is preferred over the simple A.C.generator1. Carbon brushes wear and tear easily2. The connection with the slip ring becomes loose when the carbon brushis eroded  increase the resistance at the connecting point  lessercurrent is generated as it causes unnecessary thermal energy3. The fixed coil A.C. generator design is more compact and space-savingA transformer: a device that changes a high alternating voltage (at lowcurrent) to a low alternating voltage (at high current), and vice versa_ coil A induces e.m.f. in coil B, using A.C. current_ this e.m.f. in turn drives an induced current to flow in coil BFunction of a transformer1. Electrical power transmission2. Regulating voltages for proper operation of electrical appliancesA closed-core transformer
34. 34. 34 | P h y s i c_ the lamination of the soft iron core reduces heat loss due to inducededdy currentsA step-up transformer – Vs > VpA step-down transformer – Vs < Vp***100% efficiencyCauses of power loss1. heat loss due to the resistance of the coils2. leakage of magnetic field lines between the primary and secondarycoils3. heat loss due to eddy currents induced in the iron core4. hysteresis loss caused by the flipping of magnetic dipoles in theiron core due to A.C.Reduce heat loss due to resistance1. use thicker cables2. reduce the current I, using a step-up transformer( )***Power can be transmitted more efficiently at higher voltages andlower currentsConverting A.C. to D.C. – diodesThe diode: a semiconductor device that allows a current to flow easilyin one direction only
35. 35. 35 | P h y s i cRectification: the conversion of A.C. into D.C.Half-wave rectificationFull-wave rectification – a bridge rectifier
36. 36. 36 | P h y s i cCathode-Ray Oscilloscope – C.R.O._ The electron gun emits a beam of electrons (thermonic emission) – acathode ray_ The fluorescent screen is coated with Zinc sulphide_ the Y-plates – vary the vertical position_ the Y-plates – sweep the electron beam horizontallyY-gain_ amplifies the Y-deflection so that the small input voltages areamplified before they are applied to the Y-platesTime-base_ controls the speed, at which the electron beam sweeps across thescreen horizontally from left to right– by the X-plates_ sawtooth voltage applied to the X-plates
37. 37. Physics FormulaTopic Formula SI unit Final unit2.1: Kinematics DistanceSpeedTimeDistance (m)Time (sec)m/sDisplacementVelocityTime ;svtDisplacement (m)Time (sec)m/sDiff. in VelocityAccelerationTimeCondition: Used only when acceleration isconstant.Velocity (m/s)Time (sec)m/s22.2 Dynamics Resultant Force Mass Acceleration F maForce (N)Mass (kg)Acceleration (m/s2)Newton (N)2.3 Mass WeightDensityW mg Mass (kg)g = 10 N/kgNewton (N)(Density)mV  ;.Mass (g/kg)Volume (cm3/m3)g/cm3orkg/m32.4 Turning Effectof ForcesMoments Fd Force (N)Perpendicular Distance (m)Newtonmetre (Nm)Note: Perpendicular Distance is not always the length of the rod.2.5 PressureSolids:ForcePressureAreaFA Force (N)Area (m2)N/m2, PaLiquids: Pressure h g h (m): Depth of Liquid (kg/m3): Density of liquidg: 10N/kgN/m2, PaGases (when temp. is constant)1 1 2 2PV P VP (Pa): PressureV (m3): VolumeNA2.6 Energy, Work,power(Work Done)W Fd F (N): Forced (Perpendicular dist): mJ  21. . Kinetic Energy2K E mvm (kg): Massv (m/s): VelocityJ . . Potential EnergyP E mgh m (kg): Massg: 10N/kgh (m): HeightJX  or Energy changePowerTimeWP Energy change /Work done(J)Time (s)J/s, W(watt)3.1 Principles ofThermometry0100 0X XX X(For Celsius scale only)Theta: Unknown temperatureX0: “ice point”, X100: Steam ptoC3.2 ThermalProperties ofMatter(heat energy)Q C C: Heat capacity JQ mc m: massc: Specific Heat CapacityJfQ ml fl : Latent heat of fusion JvQ ml vl : Latent heat of vapourisation J4.1: General WaveProperties1fTf: Frequencyt (sec): TimeHzv f  v (m/s): Velocity (m): Wavelengthf(1/t): Frequencym/s4.2: Light Snell’s Law:sinsininrn = refractive index (ratio)i/r (o): angle ofincidence/refraction*Set calculator in degree mode.NA. Ratio.Condition: The angle of incidence must be in the less dense medium; angle r must be in thedenser medium.
38. 38. 4.2: Light Ht of imageReal depthApparent depth Ht of objectcnv  c (m/s): Speed of light in vaccum(3x108m/s)v (m/s): Speed of light in medium.NA. Ratio.1sinc n c (o): Critical angle. o5.1: CurrentElectricityQItI: Current (A)Q: Charge (Columb)t: Time (sec)Coloumb,CWQ  : E.m.f. (Volts – V)W: Work done/energy of circuit (J)Q: Charge (Columb)V, J/CWVQV: Potential Diff. (V)W: Work done/energy acrosscircuit componentQ: Amount of chargeV, J/COhm’s Law: V IRCondition: Only for ohmic conductors.R: Resistance (  ) VlRA  m)L: LengthA: Cross-sectional Area5.2: PracticalElectricity22 V tE VIt I RTR  J22 VP VI I RR  W5.3:ElectromagneticInductionps sp p sIV NV N I 