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UP Board Class 12 Moving Charges and Magnetism — practice questions — page 2

Explore 61 free Moving Charges and Magnetism questions in UP Board Class 12 Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Moving Charges and Magnetism questions and exercises with answers

Showing questions 31–60 of 61.

A 0.1 m radius loop carries 5 A. The magnetic field at a point on its axis 0.1 m from the centre is approximately (μ₀ = 4π × 10⁻⁷ T·m/A)Read the answer and worked solution →A bar magnet with N pole pointing right is placed near a circular current loop whose magnetic moment also points right. The interaction isRead the answer and worked solution →Cyclotrons are not used to accelerate electrons becauseRead the answer and worked solution →A long solenoid has 1000 turns per metre and carries 2 A. The magnetic field strength inside isRead the answer and worked solution →A square coil of side 0.1 m, with 50 turns, carries 1 A in a 0.2 T field. The maximum torque on the coil isRead the answer and worked solution →A charge q moves with velocity v through a region with electric field E and magnetic field B. The net electromagnetic force on it isRead the answer and worked solution →Match each current to its fieldRead the answer and worked solution →Judge these claims on magnetic forceRead the answer and worked solution →The Lorentz forceRead the answer and worked solution →Work done by a magnetic forceRead the answer and worked solution →Reading the Lorentz forceRead the answer and worked solution →Force on a current wireRead the answer and worked solution →The current carrying conductorRead the answer and worked solution →Charge in a uniform fieldRead the answer and worked solution →What the cyclotron frequency ignoresRead the answer and worked solution →The cyclotron machineRead the answer and worked solution →Formula to what it describesRead the answer and worked solution →The Biot-Savart lawRead the answer and worked solution →Using Biot-SavartRead the answer and worked solution →Field of a circular coilRead the answer and worked solution →Odd one out: magnetismRead the answer and worked solution →Depends on speed or notRead the answer and worked solution →True of the magnetic forceRead the answer and worked solution →Symbol to quantityRead the answer and worked solution →Which is largerRead the answer and worked solution →Field and force directionsRead the answer and worked solution →Currents make fieldsRead the answer and worked solution →Count and computeRead the answer and worked solution →Odd one out: what a current doesRead the answer and worked solution →Zero work, changing directionRead the answer and worked solution →

Worked practice questions

A 0.1 m radius loop carries 5 A. The magnetic field at a point on its axis 0.1 m from the centre is approximately (μ₀ = 4π × 10⁻⁷ T·m/A)

  1. 1.6 × 10⁻⁵ T
  2. 2.2 × 10⁻⁵ T
  3. 3.1 × 10⁻⁵ T
  4. 1.1 × 10⁻⁵ T
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Correct answer: D. 1.1 × 10⁻⁵ T

1. Use B = μ₀IR² / (2(R²+x²)^(3/2)). 2. With R = x = 0.1 m: R²+x² = 0.02 m²; (0.02)^(3/2) ≈ 0.002828. 3. Numerator: μ₀IR² = 4π × 10⁻⁷ × 5 × 0.01 ≈ 6.28 × 10⁻⁸. 4. B = 6.28 × 10⁻⁸ / (2 × 0.002828) ≈ 1.11 × 10⁻⁵ T. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", §4.6_

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A bar magnet with N pole pointing right is placed near a circular current loop whose magnetic moment also points right. The interaction is

  1. attractive
  2. repulsive
  3. zero force
  4. torque but no force
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Correct answer: A. attractive

1. A current loop acts as a magnetic dipole; aligning moments means the loop's south pole faces the magnet's north pole. 2. Opposite poles attract in magnetic interactions. 3. The non-uniform field of the bar magnet exerts a net force on the loop. 4. The force pulls the loop toward the bar magnet, so the interaction is attractive. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", §4.10.2_

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Cyclotrons are not used to accelerate electrons because

  1. Electrons have negative charge
  2. Electron mass grows too fast with energy
  3. Magnetic field cannot deflect electrons
  4. Electrons spin too rapidly for resonance
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Correct answer: B. Electron mass grows too fast with energy

1. Cyclotron operation depends on a constant frequency f = qB/(2πm). 2. As electrons gain energy, their relativistic mass m grows rapidly because the rest mass is very small. 3. The cyclotron frequency therefore drifts, breaking resonance with the AC accelerating voltage. 4. Heavier ions tolerate higher energies before relativistic effects matter; for electrons, betatrons or synchrotrons are used instead. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", §4.4.2_

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