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JKCET Electromagnetism — practice questions — page 3

Explore 89 free Electromagnetism questions in JKCET Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Electromagnetism questions and exercises with answers

Showing questions 61–89 of 89.

A charged particle moves in a circle of radius 2 cm in a 1 T magnetic field with speed 4 × 10⁶ m/s. Mass-to-charge ratio m/q:Read the answer and worked solution →For a current loop in a non-uniform magnetic field, net force is zero only if:Read the answer and worked solution →Earth's magnetic field is approximately 50 μT. Force on a 1 m wire carrying 10 A perpendicular to field:Read the answer and worked solution →A toroid with 1000 turns and average radius 10 cm carries 0.5 A current. Field inside:Read the answer and worked solution →Two parallel wires carrying currents in OPPOSITE directions:Read the answer and worked solution →A magnetic dipole of moment m in field B has potential energy:Read the answer and worked solution →Complete the work-energy theoremRead the answer and worked solution →True or false: conservative forcesRead the answer and worked solution →Conservative or not?Read the answer and worked solution →Reading the theoremRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Tap every test for a conservative forceRead the answer and worked solution →Order the reasoning: from work to speedRead the answer and worked solution →Flip and pair: term with meaningRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →True or false: energy bookkeepingRead the answer and worked solution →Speeds up, slows down, or neither?Read the answer and worked solution →Applying the work-energy theoremRead the answer and worked solution →True or false: potential energyRead the answer and worked solution →Kinetic or potential?Read the answer and worked solution →Tap every statement true of a closed pathRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Assertion and reason: energyRead the answer and worked solution →Complete the potential energy relationRead the answer and worked solution →Flip and pair: quantity with what it tracksRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Order the reasoning: why a pendulum keeps swingingRead the answer and worked solution →Conservative or not, in practiceRead the answer and worked solution →

Worked practice questions

A charged particle moves in a circle of radius 2 cm in a 1 T magnetic field with speed 4 × 10⁶ m/s. Mass-to-charge ratio m/q:

  1. 5 × 10⁻⁹ kg/C
  2. 5 × 10⁻⁸ kg/C
  3. 2.5 × 10⁻⁸ kg/C
  4. 8 × 10⁻⁹ kg/C
Show answer and solution

Correct answer: A. 5 × 10⁻⁹ kg/C

r = mv/(qB). **So m/q = rB/v = (0.02)(1)/(4 × 10⁶) = 5 × 10⁻⁹ kg/C. For comparison, electron m/e ≈ 5.7 × 10⁻¹² kg/C (much smaller, meaning electron mass is light).**

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For a current loop in a non-uniform magnetic field, net force is zero only if:

  1. Field is zero
  2. Field is UNIFORM (constant in space)
  3. Loop is small
  4. Current is small
Show answer and solution

Correct answer: B. Field is UNIFORM (constant in space)

In uniform B, all parts of the loop experience equal and opposite forces — net force zero (but torque can be nonzero). In non-uniform B, opposite sides of loop see different B, leading to net force (causes a magnetic dipole to be pulled toward higher field regions for an aligned moment).

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Earth's magnetic field is approximately 50 μT. Force on a 1 m wire carrying 10 A perpendicular to field:

  1. 5 × 10⁻⁴ N
  2. 5 × 10⁻⁶ N
  3. 50 N
  4. 5 N
Show answer and solution

Correct answer: A. 5 × 10⁻⁴ N

F = BIL sin theta = (50 × 10⁻⁶)(10)(1)(1) = 5 × 10⁻⁴ N = 0.5 mN. Small but measurable.

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