JEE Physics - Electromagnetic induction and alternating currents

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Question - 1

A rectangular loop of width l is placed in a uniform magnetic field \(\overrightarrow { B } \), at right angle to the plane of the loop. It is pulled with a force F from side l so that it moves with a uniform velocity \(\vartheta \).the ohmic resistance of the loop is R=5 ohm,l=0.10m,B=0.2T, and \(\vartheta \)=15 cm \(??{ s }^{ -1 }\). the current induced in the loop is:

  • A 6 mA
  • B 6\(\mu A\)
  • C 0.6 mA
  • D 60 mA

Question - 2

As follows from question 3, the rate of joule heating in the loop is

  • A \(1.8\times { 10 }^{ -6 }W\)
  • B \(1.8\times { 10 }^{ -4 }W\)
  • C \(1.8\times { 10 }^{ -2 }W\)
  • D \(1.8\times { 10 }^{ -8 }W\)

Question - 3

A coil of wire is rotated in a uniform magnetic field.

  • A A direct current of constant e.m.f is produced
  • B An alternating e.m.f of constant amplitude is produced
  • C An alternating e.m.f of varying frequency is produced
  • D A direct current of varying e.m.f is produced

Question - 4

Lenz's law is a consequence of 

  • A law of conservation of charge
  • B law of conservation of energy
  • C retarding force and ohm's law
  • D magnetic effect of current

Question - 5

Two identical coils each of inductance L are equivalent to a total inductance of 2H when connected in parallel.The value of L for each coil is:

  • A 1H
  • B 2H
  • C 4H
  • D 6H

Question - 6

Three metalic loops of copper,platinum and sliver having exactly the same dimension,are rotating in a uniform magnetic field with the same angular velocity.The induced e.m.f is

  • A maximum in copper loop
  • B maximum in platinum loop
  • C maximum in sliver loop
  • D same in all the loops

Question - 7

The current through a coil of inductance 2H falls from 5 A to 4 A in one second. The e.m.f developed across the coil is

  • A -2V
  • B 2V
  • C -10V
  • D 10V

Question - 8

The direction of induced e.m.f can be found by

  • A Fleming's left-hand rule and Lenz's law
  • B Fleming's right-hand rule
  • C Right hand thumb rule
  • D Maxwell's cork-screw rule

Question - 9

The parallel LC circuit acts as a simple harmonic oscillator due to the exchange of

  • A Kinetic and potential energy
  • B velocity of positive and negative charge
  • C electric and magnetic energy
  • D electric energy in C and magnetic energy in L.

Question - 10

In a D.C motor the direction of force on the sides of the coil can be found by

  • A Fleming's left-hand rule
  • B Fleming's right-hand rule
  • C SNOW rule
  • D Ampere's swiming rule
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