1. Chapter wise Theoretical Important Questions inPhysics for Class-XII
Electrostatics-
1. Derive an expressionforthe electricfieldata pointon the axial positionof an
electricdipole.
2. Derive an expressionforthe electricfieldata pointon the equatorial positionof an
electricdipole.
3. Describe the Principle,constructionandworkingof Vande Graff generator.
4. Derive an expressionforthe energystoredinacapacitor.Show that whenevertwo
conductorsshare charges bybringingthemintoelectrical contact,there isalossof
energy.
5. Derive an expressionforthe effectivecapacitance whencapacitorsare connected
in(a) seriesand(b) parallel
6. Explainthe principle of acapacitorand derive anexpressionforthe capacitance of
a parallel plate capacitor.
7. State Gausstheoremandapplyit to findthe electricfieldata pointdue to (a) a
line of charge (b) A plane sheetof charge (c) A Chargedspherical conductingshell
8. State Coulomb'slawandexpressitinvectorform.Derive itusingGausstheorem.
9. Derive an expressionforthe torque onanelectricdipole inauniformelectricfield.
10.Derive an expressionforthe workdone inrotatingan electricdipoleinauniform
electricfield
11.Derive an expressionforthe energystored (Potential Energy)inadipole ina
uniformelectricfield.
12.Derive an expressionforthe electrostaticpotential energyof asystemof point
charges
13.Derive an expressionforthe capacitance of a parallel plate capacitorwith(a) a
dielectricslab(b) ametallicplate inbetweenthe platesof the capacitor.
14.Define electricpotential atapoint.Derive anexpressionforthe electricpotentialat
a pointdue to (a) a pointcharge (b) a systemof pointcharges(c) a dipole.
15.Show thatthe workdone inan electricfieldisindependentof path.
16.What are dielectrics?Distinguishpolarandnonpolardielectrics.Define the term
Polarizationvector.
2. Current Electricity-
1. Define driftvelocityandderive anexpressionforit.
2. Derive the expression I=nAevd
3. Deduce Ohm'slaw fromelementaryideasandhence write anexpressionfor
resistance andresistivity.
4. Derive an expressionforconductivityintermsof mobility
5. Explainthe colorcodingof carbon resistors.
6. Derive an expressionforthe currentina circuitwithexternal resistance Rwhen(a)
n identical cellsof emf Eandinternal resistance rare connectedinseries(b) m
identical cellsare connectedinparallel
7. State andexplainKirchhoff’slaws.
8. State andexplainthe principle of WheatStone'sprinciple.Deduce itusing
Kirchhoff’slaws.
9. Describe howyouwill determine the resistance of agivenwire usingMeter
Bridge.
10.Explainthe principle of apotentiometer.Describe how will youdetermine (a) the
ratioof emfsof two primarycellsusingpotentiometer.(b) The internal resistance
of a primarycell usingpotentiometer.
11.Explainthe variationof resistance andresistivitywithtemperature andhence
define temperature coefficientof resistance andresistivity.
MagneticEffect of Current
1. State Biot- Savartlawand applyit to findthe magneticfielddue toa circularloop
carryingcurrent at a point(a) at itscentre (b) on the axis
2. State Ampere'scircuital lawandapplyitto findthe magneticfield(a) insidea
currentcarrying solenoid(b) insideacurrentcarryingtoroid
3. ApplyAmpere'scircuital lawtodeterminethe magneticfieldata pointdue to a
longstraightcurrentcarrying conductor.
4. Derive an expressionforthe force ona current carryingconductorin a uniform
magneticfield
5. Derive an expressionforthe force betweenlongstraightconductorscarrying
currentand hence define 1ampere
3. 6. Derive an expressionforthe torque ona currentcarrying loopina uniform
magneticfield.
7. Describe the principle constructionandworkingof aMoving coil galvanometer.
8. Describe the conversionof amovingcoil galvanometerinto(a) Ammeter(b)
Voltmeter
9. What is radial magneticfield?Whatisitsimportance inamovingcoil
galvanometer?Howisaradial magneticfieldrealizedinmovingcoil
galvanometers?
10.Describe the principle constructionandworkingof acyclotron.Explainwhyan
electroncannotbe acceleratedusingacyclotron.
11.Describe the motionof a charged particle ina magneticfieldwhenitentersthe
field(a) perpendiculartothe fieldlines(b) obliquelymakingandangle Θwiththe
fieldlines
12.Derive an expressionforthe magneticdipole momentof arevolvingelectronand
hence define Bohrmagneton.
ElectromagneticInduction(EMI)-
1. State andExplainFaraday'slawsof electromagneticinduction.()
2. State Lenz'Law and showthat itis inaccordance withthe law of conservationof
energy.
3. Use Lenz' lawto findthe directionof inducedemf inacoil when(a) a northpole is
broughttowardsthe coil (b) north pole takenawayfromthe coil (c) A southpole is
broughttowardsthe coil and (d) a south pole istakenawayfromthe coil,Draw
illustrationsineachcase.
4 What ismotional emf.Deduce anexpressionforit.State Fleming'sright handrule
to findthe directionof inducedemf.
5. What are eddycurrents?Describe the applicationsof eddycurrents.
6. Explainthe workingof (a) ElectromagneticBrakes(b) InductionFurnace
7. Which physical quantityiscalledthe INERTIA OF ELECTRICITY?Why isits
calledso?
8. Define self inductionandself inductance.Whatisitsunit?Write itsdimensions.
9. Derive an expressionforthe self inductance of alongsolenoid.
4. 10.Explainthe phenomenonof mutual inductionanddefine mutualinductance.Write
the unitand dimensionsof mutual inductance.
11.What are the factorsaffectingmutual inductance of apairof coils?Define
coefficientof coupling.
12.Describe the variousmethodsof producinginducedemf.Deriveanexpressionfor
the instantaneousemf inducedinacoil rotatedina magneticfield.
13.What isdisplacementcurrent?Explainitsneed.
Alternative Current-
1. Describe the principle constructionandworkingof anAC generator.Draw neat
labeleddiagram
2.Define meanvalue of AC(overahalf cycle) andderive anexpressionforit.
3. Define RMS value of ACand derive anexpressionforit.()
4. Showthat the average value of ACovera complete cycle iszero.
5. Showthat the currentand voltage are inphase inan ac circuitcontainingresistance
only.
6. Deduce the phase relationshipbetweencurrentandvoltage inanac circuit
containinginductoronly.
7. Deduce the phase relationshipbetweencurrentandvoltage inanac circuit
containingcapacitoronly.
8. Draw the phasordiagram showingvoltage andcurrentinLCR seriescircuitand
derive anexpressionforthe impedance
9. What do you meanbyresonance inSeriesLCRcircuit?Derive anexpressionfor
the frequencyof resonance inLCRcircuit.
10.Distinguishbetweenresistance, reactance andimpedance.
11.Define qualityfactor(Qfactor) of resonance andderive anexpressionforit.
12.Describe the mechanismof electromagneticoscillationsinLCcircuitand write
expressionforthe frequencyof oscillationsproduced.
13.Derive an expressionforthe average powerinanac circuit.
14.Define powerfactor.Deduce expressionforitandexplainwattlesscurrent?
15.Describe the principle constructiontheoryandworkingof atransformer.
16.Describe the variouslossesinatransformerandexplainhow the lossescanbe minimized.
5. ElectromagneticWaves-
1. Explainthe inadequacyof Ampere'scircuital law
2. Describe Hertzexperimenttodemonstrate the productionof electromagnetic
waves
3. Write the propertiesof electromagneticwaves.
4. Write anyfive electromagneticwavesinthe orderof decreasingfrequencyand
write anytwo propertiesandusesof each
5. Deduce an expressionforvelocityof emwavesinvacuum
6. Establishthe transverse nature of electromagneticwaves.
7. Compare the propertiesof electromagneticwavesandmechanical waves
Ray-Optics-
1. Derive mirrorformulafora concave mirrorand convex mirror.
2. Derive an expressionforlateral shiftandnormal shift.Onwhatfactorsthese
depend.
3. Define TIRand write the conditionsforTIR.Derive arelationbetweencritical
angle andthe refractive indexof the medium.Alsoexplainthe workingof
isoscelesprismandoptical fiber.
4. Derive the followingrelationforareal image formedbya convex refracting
surface whenthe objectisplacedinrarer medium.Alsowrite the assumptionsand
signconventionused.
5.2 1 2 1
v u R
6. Derive the lensmaker’sformula.Alsowrite the assumptionsandsignconvention
used.
7. Derive the lensformulaforconvex lendand concave lens.
8.Derive the relationforequivalentfocal lengthorpowerwhentwothinlensesare
placedincontact to each other.Inwhichconditionthe lenscombinationwill actas
a plane glasssheet.
10.Where the symbolshave theirusual meanings.
6. 11.Draw a ray diagramto showthe image formationinrefractingtype astronomical
telescope inthe nearpointadjustment(whenimage isformedatLDDV i.e.
D=25cm). Derive anexpressionforitsmagnifyingpower.Whythe diameterof
objective of telescopeshouldbe large.
12.Draw a ray diagramto showthe image formationinrefractingtype astronomical
telescope inthe normal adjustment(whenimage isformedatinfinity).Derive an
expressionforitsmagnifyingpower.How doesthe magnifyingpowergetaffected
on increasingthe aperture of the objective lensandwhy?
13.Draw a ray diagramto showthe image formationa compoundmicroscope.Explain
brieflythe working.Derive anexpressionforitsmagnifyingpower.Whythe
diameterof objectiveof microscope should be small.
14.Draw a labeleddiagramof areflectingtype telescope.State twoadvantagesof this
telescope overrefractingtype telescope.
15.Define resolvingpowerof compoundmicroscope.How doesthe resolvingpower
of a compoundmicroscope change when-(a) Refractiveindex of mediumbetween
the objectand objective lensincreases(b) Wavelengthof the lightusedis
increased(c) decreasingthe diameterof objective(iv) increasingthe focal length
of itsobjective.
16.Define the resolvingpowerof astronomical telescope.Write the expressionforit
and state,onwhat factorsit depends
Wave-Optics-
1. Define wave front.State Huygensprinciple andverifySnell’slaw.
2. State Huygensprincipleandprove the lawsof reflectiononthe basisof wave
theory.
3. What do you meanbyinterference of light?Explaininbrief the Young’sdouble
slitexperiment.
4 What are the coherentsources?Write the conditionsforthe sustainedinterference
pattern.Alsodrawthe intensityv/spathdifference curve.
5. Findthe conditionsforconstructive anddestructive interference.How doesthe
intensitydependonthe widthof slit?
6. Findthe expressionforthe fringe width.Whatisthe effectonthe fringe widthif
7. the whole apparatus(YDSE) iscompletelyimmersedinaliquidof refractive index
μ?
7. What do you meanbydiffractionof lightandstate the conditionforthe
diffraction?Obtainthe conditionsforsecondarymaximaandminima.Alsodraw
the intensitydistributioncurve.
8. Prove that the widthof central maxima istwice the widthof the secondary
maxima.Howdoesthe widthof central maximadependonthe widthof the slit?
9. State Brewster’slawandprove thatthe reflectedandrefractedraysare mutually
perpendicularatthe angle of polarization.
10.State law of Malusand draw an intensityV/sanglebetweenthe plane of
transmissionof polarizerandanalyzer.
11.What isa Polaroid?Howare theyconstructed?Mentiontheirimportant
applications.
12.ExplainPolarizationof light.Give anyone methodtoproduce plane polarized
light.
Dual Nature of Radiation-
1. Describe the experimenttostudyphotoelectriceffectandexplainthe lawsof
photoelectriceffectandthe significance of each.
2. Describe Hertzand Lenard’sexperimenttodemonstratephotoelectric effect.
3. explainEinstein'sphotoelectricequationandexplainthe lawsof photoelectric
effectusingit.
4. State andexplainde Broglie relationformatterwaves.
5. Describe Davisson- Germerexperimentwhichprovidedexperimentalevidence for
wave nature of matter.
6. Write the characteristicsof Photon.
SemiconductorDevices-
1. Distinguishbetweenconductors,insulatorsandsemiconductorsonthe basisof
energybands.
2. What are extrinsicsemiconductors?Mentionitstypesandexplainthe mechanism
of conductionineach.
3. Explainthe conductioninN Type and P Type semiconductoronthe basisof band
8. theory.
4. Explainthe formationof depletionlayerandpotential barrierina PN junction
diode.
5. Draw the circuitdiagramusedto determine the VIcharacteristicsof adiode and
draw the forwardand reverse biascharacteristicsof adiode.Explainthe
conclusionsdrawnfromthe graph.
6. With the helpof a labeledcircuitdiagramexplainthe workingof half wave
rectifieranddrawthe inputand output waveforms.
7. With the helpof a labeledcircuitdiagramexplainthe workingof full wave rectifier
and drawthe inputandoutputwaveforms.
8. Write notesonLED, photodiode andsolarcell.
9. What is a Zenerdiode?Drawthe VIcharacteristicsof zenerdiode.ExplainZener
breakdownanddescribe the use of a zenerdiode asa voltage regulator.
10.Explainthe actionof a PNPtransistorandan NPN transistor.(Explainhow
conductiontakesplace inNPN andPNPtransistor.)
11.Draw the circuitdiagramfor determiningtransistorcharacteristicsanddescribe the
inputandoutput characteristicsof transistorinCB configurationwithrelevant
graphs.
12.Draw the circuitdiagramfor determiningtransistorcharacteristicsanddescribe the
inputandoutput characteristicsof transistorinCE configurationwithrelevant
graphs.
13.Explainthe workingof TransistoramplifierinCEconfigurationwithnecessary
circuitdiagram.
14. Explainthe workingof transistoroscillator.
15. Explainthe workingof transistoras a switch.
16. Draw the symbol,truthtable andBooleanexpressionforOr,ANDandNOT gate.
17. Draw the symbol andtruth table of NORgate and NANDgate.
18.Explain,howthe fundamental logicgatescanbe realizedusingNORgatesalone.
19. Explainhowthe fundamentallogicgatescanbe realizedusingNANDgatesalone.
PrinciplesofCommunication-
1. Derive an expressionforthe range of transmissionviaspace wave froma
9. transmittingantennaof heighth.
2. Describe radiowave propagationvia(a) GroundWave (b) Space Wave and
(c) Sky Wave.
3. What is the needforsatellite communication?Elaborate.
4. Explainthe needformodulationforlongdistance transmission.
5. Define amplitude modulationandillustrateitusingdiagrams(graphs)
6. Define modulationindex andwrite itsexpression.
7. What are the advantagesand disadvantagesof FMoverAM?
8. Explainthe role of repeaterincommunication
9. Describe the mechanismof demodulation(detection) of AMWave usingblock
diagram,circuitdiagramand graphical representation
10.What isLOS communication?
11.What are the basicelementsof acommunicationsystem?Explainthe functionof
each.
12.Draw the blockdiagramof a communicationsystem.
