XIIth PHYSICS (C2, G2, C, G) Solution

Transcription

1 XIIth PHYSICS (C, G, C, G) -6- Solution. A 5 W, 0 V bulb and a 00 W, 0 V bulb ae connected in paallel acoss a 0 V line nly 00 watt bulb will fuse nly 5 watt bulb will fuse Both bulbs will fuse None of the bulbs will fuse. An electic bulb is ated 0 volt and 00 watt. Powe consumed by it when opeated on 0 volt is 50 watt 75 watt 90 watt 5 watt. If two bulbs of wattage 5 and 00 espectively each ated at 0 volt ae connected in seies with the supply of 0 volt, then which bulbs will fuse 00 watt bulb 5 watt bulb None of them Both of them. If cuent in an electic bulb changes by %, then the powe will change by % % % % 5. Accoding to Joule's law, if the potential diffeence acoss a conducto having a mateial of specific esistance emains constant, then the heat poduced in the conducto is diectly popotional to 6. A 0 V stoage battey of negligible intenal esistance is connected acoss a 50 esisto. How much heat enegy is poduced in the esisto in hou 700 J 600 J 500 J 00 J 7. The maximum cuent that flows though a fuse wie befoe it blows out vaies with its adius as / / / 8. What is immateial fo an electic fuse wie Specific esistance of the wie adius of the wie Length of the wie Cuent flowing though the wie 9. Find the powe of the cicuit V.5 W W W None of these 0. In the cicuit, shown in fig. K is open. The chage on capacito C in steady state is q. Now key is q closed and at steady state, the chage on C is q. The atio of chages q E C K is

2 . The magnetic field d B due to a small cuent element d l at a distance and element caying cuent i is, Vecto fom of Biot-savat's law is 0 dl db i db dl 0 i o 0 db i db dl 0 dl i. A chage q coulomb moves in a cicle at n evolutions pe second and the adius of the cicle is mete. Then magnetic field at the cente of the cicle is q 0 n q N/amp/mete N/amp/mete nq 0 7 N/amp/mete q N/amp/mete. An infinitely long staight conducto is bent into the shape as shown in the figue. It caies a cuent of i ampee and the adius of the cicula loop is mete. Then the magnetic induction at its cente will be 0 i ( ) 0 i ( ) Zeo Infinite. A cuent i ampee flows in a cicula ac of wie whose adius is, which subtend an angle / adian at its cente. The magnetic induction B at the cente is 0 i 0 i 0 i 0 i 8 i 5. A staight section PQ of a cicuit lies along the X-axis fom The magnetic field due to the section PQ at a point X = + a will be / i x a to a x and caies a steady cuent i. Popotional to a Popotional to a Popotional to / a Zeo 8 6. The magnetic induction at a point P which is distant cm fom a long cuent caying wie is 0 Tesla. The field of induction at a distance cm fom the same cuent would be 9. 0 Tesla. 0 Tesla 0 Tesla 9 0 Tesla

3 7. A cuent of 0. A ciculates aound a coil of 00 tuns and having a adius equal to 5 cm. The magnetic field set up at the cente of the coil is 7 ( 0 0 webe / ampee mete) tesla 8 0 tesla 0 tesla 0 tesla 8. In the figue, shown the magnetic induction at the cente of thee ac due to the cuent in potion AB will be 0 i 0 i 0 i Zeo 9. In the above question, the magnetic induction at due to the whole length of the conducto is 0 i 0 i 0. In the figue shown thee ae two semicicles of adii and in which a cuent i is flowing. The magnetic induction at the cente will be ) ( ( ) A B C D. The magnetic induction at the cente in the figue shown is 0 i 5 Zeo 5. Cuent in esisto is (see given figue) A.5 A 0.9 A 0.6 A

4 . In the cicuit shown in figue, with steady cuent, the potential dop acoss the capacito must be V V V V. The numeical value of chage on eithe plate of capacito C shown in figue CE CE CE CE 5. Two electic bulbs (60W and 00W espectively) ae connected in seies. The cuent passing though them is Moe in 00W bulb Moe in 60W bulb Same in both None of these 6. Two electic bulbs ated watt V volts and watt V volts ae connected in paallel and V volts ae applied to it. The total powe will be P P watt P P P P P P watt watt P P P P watt 7. All the edges of a block with paallel faces ae unequal. Its longest edge is twice its shotest edge. The atio the maximum to minimum esistance between paallel faces is 8 indeteminate unless the length of the thid edge is specified 8. A nonconducting ing of adius has chage Q distibuted unevenly ove it. If it otates with an angula velocity, the equivalent cuent will be Q Q zeo Q

5 9. Two capacitos C and C = C ae connected in a cicuit with a switch between them as shown in the figue. Initially the switch is open and C holds chage Q. The switch is closed. At steady state, the chage on each capacito will be Q Q Q, Q, Q Q Q,Q, 0. A simple pendulum has a length l, mass of bob m. The bob is given a chage q. The pendulum is suspended between the vetical plates of the chaged paallel plate capacito. If E is the field stength between the plates, the time peiod T equals g qe g m g qe m g qe m SLUTINS. Because given voltage is vey high V 0 0. esistance of the bulb = 8 00 P atate When connected with 0 V, the powe consumed V 0 0 P Consumed 5W 8

6 esistance of 5 W bulb 96. P i 0 96 Its safe cuent 0. amp. esistance of 00 W bulb 0 8 Its safe cuent 0.8 amp (96 8) When connected in seies to 0 V supply, then the cuent I 0.8 amp. Thus cuent is geate fo 5 W bulb, so it will fuse. P i P t % change in powe ( Constant) % change in cuent = % 5. P V but P. l A V P l / A AV l. Since AV l is constant as pe given conditions So V Enegy t J / 7. It is called safe cuent and is popotional to In steady state the banch containing capacitos, can be neglected. So educed cicuit is as follows V Powe V () P W. 0. When key is open, chage in steady state will be q CE. When key is closed, potential diffeence acoss capacito will be Chage in steady state will be q q CE q. V E

7 0 idl sin. db i( dl db 0 ). The magnetic field at the cente of the cicle i 7 ( nq) nq N / A m. The given shape is equivalent to the following diagam The field at due to staight pat of conducto is o i B.. The field at due to cicula coil is B 0 i.. Both fields will act in the opposite diection, hence the total field at. o i o i i.e. B B B ( ). ( ) i 0 ( ) i 0. B 0 5. Magnetic field at a point on the axis of a cuent caying wie is always zeo. Y P i Q M a a x x x =a i i i 8 6. B 0 i B. 0 8 B 0 B B 9 Tesla B 0 0 Ni Tesla 8. The magnetic induction at due to the cuent in potion AB will be zeo because lies on AB when extended. 9. The induction due to AB and CD will be zeo. Hence the whole induction will be due to the semicicula pat BC. B oi 0. The magnetic induction due to both semicicula pats will be in the same diection pependicula to the pape inwads. B B B. In the following figue, magnetic fields at due to sections,, and ae consideed as B, B, B and B espectively. B B 0

8 B B 0 i. So B.. 0. i As B net B B B B net

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