CBSE Smle Per 2 Generl Instruction:. Answer ll questions 2. Internl choices re rovided for some questions 3. Question numbers to 8 re very short nswer questions nd crry mrk ech. 4. Question numbers 8 to 8 re short nswer questions nd crry 2 mrks ech. 5. Question numbers 9 to 27 re lso short nswer questions nd crry 3 mrks ech. 6. Question numbers 28 to 30 re long nswer questions nd crry 5 mrks ech. 7. Use log tbles if necessry. Very Short Answer tye questions Question A shericl conducting shell of inner rdius R nd outer rdius R2 hs chrge Q A chrge q is lced t the center of the shell.wht is the surfce chrge density on the inner nd outer surfces of the shell Question 2 Find the unit of secific conductivity Question 3 Three electric lms A,B nd C re mrked (220V,00W),(220V,60W) nd (220V,40W). Write down the lms in decresing order of their resistnce? Question 4 Find the inductnce of the inductor tht would hve rectnce of 50 ohm when used with n.c source of frequency (0/π) khz. Question 5 Wht is the resolving ower of microscoe? Question 6 The mximum KE of the electrons emitted in hotocell is 0eV. Wht is the stoing otentil? Question 7 Wht is frequency modultion? Question 8 Why is the conductivity of n tye semi conductor greter thn -tye semiconductor even when both of these hve sme level of doing?
2 Short Answer tye questions Question 9 With the hel of digrm,show the bising of light emitting diode (LED). Give its two dvntge over conventionl incndescent lms Question 0 A bulb is connected in series with vrible ccitor ) Will the bulb glow when connected to DC source suly? b) Will the bulb glow when connected to AC source suly c) wht will be the effect on both the bove if the ccitnce is reduced Question i)an electron bem sses through certin of crossed electric nd mgnetic field of intensities E0 nd B0 resectively, for wht vlue of electron seed,will the bem remins undeflected? ii) A bem of lh rticles nd of rotons of sme kinetic energy enters uniform mgnetic field t right ngles to the field lines. The rticles describe circulr ths. Clculte the rtio of the two ths Question 2 Stte Frdy s lw of electromgnetic induction. Exress it mthemticlly. Question 3 Connect three ccitors of 3µF, 3µF nd 6µF such tht their equivlent ccitnce is 5 µf Question 4 Drw circuit digrm of common-emitter mlifier using n--n trnsistor. Prove tht in this mlifier, the outut voltge is 80 0 out of hse with the inut voltge. Question 5 Wht is Wien s dislcement Lw? Question 6 A oint chnge q is surrounded by shericl Gussin surfce of rdius r nd now if the shere is relced by the cube of side r,will the electric flux through this surfce will be lrger then shericl surfce?. Exlin Question 7 In cr srk coil,when the current in the rimry is reduced from 4.0 A to zero in 0µs,n emf of 40,000 V is induced in the secondry. Find the mutul inductnce M of the rimry nd secondry winding of the srk coil?
3 Question 8 In common emitter mlifier the lod resistnce of the outut circuit is 000 times the lod resistnce of the inut circuit. If α.98,the clculte the voltge gin Question 9 Wht is trnsistor? Describe the working n--n trnsistor.why is it more useful in comrison to -n- trnsistors? Question 20 The hlf life of rdium is 600 yers.after how mny yers 25% of rdium block remins undecyed? Question 2 Wht is the th of the chrged rticle in the uniform mgnetic field if its velocity is not erendiculr to the mgnetic field? Exlin Question 22 Exlin the mening of hoto electric work function by giving necessry eqution? Question 23 When current flows in the coil of trnsformer, its core become hot? Question 24 Two inductnce L nd L2 re connected in rllel nd re serted by lrge distnce. Find the equivlent inductnce of the rrngement? How will the result be ffected if the sertion is not lrge? Question 25 The energy of n electron in n excited hydrogen tom is -3.4 ev. Clculte the ngulr momentum of the electron ccording to Bohr s theory Plnk constnt (h) 6.626X0-34 J-s Question 26 The resistnce of tungsten filment t 50 0 C is 33 ohm. Wht will be the resistnce t 500 0 C? The temerture coefficient of resistnce of tungsten is 0.0045 er 0 C. Question 27 Two bulbs re mrked 60W-220 V nd 00W-220V. They re connected in rllel to the 220V mins. Which bulb will glow brighter? if the one of the bulb is switched off,will the light in the room increse or decrese? Question 28 i)wht re eddy currents? how re they roduced? Give two lictions of eddy current? ii) A metl lte oscilltes bout horizontl xis.a strong mgnetic field is lied on the oscillting lte. Wht will hen?
4 Question 29 i) Define ccitnce. Derive n exression for the ccitnce of rllel lte ccitor. ii) Find out the energy density in rllel lte ccitor in terms of electric field between the ltes Question 30 Exlin the construction.rincile nd working of DC motor.find its efficency?
5 Solutions Solution Uniform on both inner nd outer shell Solution 2 Ohm - m - Solution 3 2 V P R As V is constnt Pα R So resistnce in decresing order C>B>A Solution 4 X L 2πνL Or 3 XL 50X0 3 L 2.5X0 H 2πν 0 2π ( ) π Solution 5 Resolving ower of the microscoe 2µ sinθ.22λ Where µ is the refrctive index of the medium between the object nd objective lens,θ is the semi solid ngle of the cone of light subtended by the oint object on the objective Solution 6 2 mv ev0 2 So V00 V Solution 8 In n-tye of semi-conductor, the conduction is due to electrons while -tye conductor hs holes for conduction. The mobility of electron re higher for electrons then holes so tht whys n-tye re more conductive then tye semiconductor Solution 0 ) No current will flow in the circuit s the ccitor offer infinite rectnce ( Xc/ωC s ω0 for DC circuit
6 And this will not chnge if we reduce the ccitnce lso b) Current will flow in the circuit s ccitor offers finite rectnce.on reducing ccitnce,rectnce will increse thereby decresing the current in the circuit nd bulb will glow less brightly Solution i) When the electron sses undeflected through mutully erendiculr electric nd mgnetic field then Then Electric force Lorentz force ee0evb0 or ve0/b0 ii) The rdius of circulr th followed by chrged rticle in uniform mgnetic field B is given by mv r qb Now if K is the kinetic energy,then 2 2 2 m v K mv 2 2m mv So rdius r 2mK 2mK qb So for rotons r 2m q B K For lh rticles r 2m q B K Now m m 4 q q 2
7 So r r Solution 3 Ccitor connected in rllel give mximum equivlent ccitnce nd in series gives minimum equivlent ccitnce, Thus C 3+ 3+ 6 2µF mx C C min min 3 6 5 + 3 + 6.2µ F 5 6 The required ccitnce 5µF is between Cmx nd Cmin. Let it is C C 5µ F 3µ F+ 2µ F 3µ F + + 3 6 Thus we shll connect 3µF nd 6 µf in series nd the remining 3µF in rllel of the series combintion Solution 6 The electric flux deends only on the chrge enclosed by the gussin surfce, not on the she of the surfce. Φ will be the sme for the cube s for the shere Solution 7 The emf induced in the secondry is given by i e2 M t i Where is the rte of chnge of current in the rimry,thus t e2 M i / t Substituting the vlues given in question,we get M.H Solution 8 α.98 β 49 α.98 Therefore Voltge gin is given by
8 R2 3 V gin β 49X000 49X0 R Solution 20 Suose the initil quntity of rdium is N0.Then the quntity left fter n hlf lives will be N N 0 2 Now here N25% of N0N0/4 So N 0 N 4 Or n2 0 2 n n Therefore time of disintegrtion hlf-life X number of hlf lives 600X23200 yers Solution 2 The velocity vector cn be broken into horizontl nd verticl comonents rllel nd erendiculr to the mgnetic field. The velocity vector rllel to mgnetic field results in no force nd thus remin constnt. The velocity comonents erendiculr to the mgnetic field results in circulr motion bout the field lines.putting these two motion together roduces helicl motion round the field lines Solution 25 In hydrogen ton,the energy of electron is the nth energy level is 3.6 ev n E n 2 Here En.3,.4 ev,from this we n2 According to Bohr s Model,the ngulr momentum of the electron is h 34 n 2.X0 J s 2π Solution 26 If the resistnce of wire t 0 0 C be R0 nd t t 0 C be Rt, then RtR0(+αt)
9 Or, Rt R0 +α t Where α is the temerture coefficient of resistnce. The resistnce of filment t 50 0 C is 33 ohm. Therefore its resistnce t 0 0 C will be 33 R0 79. 0ohm + (0.0045) 50 Now the resistnce of filment t 500 0 C will be R R + α ) 257Ω 500 0 ( t500 Solution 27 00W bulb