Important Questions for Class 12 Physics Chapter 4 are compulsory for students preparing for CBSE 12th board exams. The 12th Physics board exam is scheduled on February 20, 2026.
Students preparing for the Physics board exam must thoroughly revise Moving Charges And Magnetism Class 12 Important Questions to strengthen conceptual clarity and numerical accuracy. The chapter includes magnetic force on a moving charge, force between parallel current-carrying conductors, torque on a current loop, and the working of a cyclotron.
Moving Charges And Magnetism Class 12 Important Questions
The chapter Moving Charges and Magnetism requires strong conceptual clarity along with practice of direction-based problems. Students must carefully revise Moving Charges And Magnetism Class 12 Solutions, especially questions involving magnetic force, circular motion of charged particles, and torque on a current loop.
Below are the Moving Charges And Magnetism Class 12 Question Answers for exam preparation:
1. A proton is moving in a space with constant velocity in an electric field E and magnetic field B. The angle between electric field and magnetic field should be [Delhi 2015]
(A) 0°
(B) 30°
(C) 45°
(D) 90°
Sol. (D)
When a charged particle (i.e., proton) is moving in space with a constant velocity in electric field E and magnetic field B, then angle between electric field and magnetic field should be 90°. Thus (D) is correct option.
2. Magnetic field due to a long straight conductor of length l, carrying current I, at a point, distance d from it is given by
Sol. (A)
Length of the straight conductor = l
Current in the conductor = I
and distance of the point from it = d
The magnetic field at a point due to a long current-carrying conductor,
3. On connecting a battery to the two corners of a diagonal of a square conductor frame of side a, the magnitude of magnetic field at the centre will be
Sol. (A)
When a battery is connected two corners of a diagonal of a square conductor frame, then the conductor frame can be taken as two sets of parallel wires carrying currents in the same direction.
Magnetic field at the centre due to two parallel wires carrying currents in the same direction will be equal in magnitude, but opposite in directions. Therefore, magnitude of the magnetic field at the centre will be zero. Thus (A) is correct option.
4. A square coil OPQR of side a carrying a current I, is placed in the Y-Z plane as shown here. Find the magnetic moment associated with this coil.
5. Explain, giving reasons, the basic difference in converting a galvanometer into (1) a voltmeter and (2) an ammeter. [Foreign 2010]
Sol. 1. In converting a galvanometer into a voltmeter, a very high suitable resistance is connected in series to its coil. So, the galvanometer gives full scale deflection.
2. In converting a galvanometer into an ammeter, a very small suitable resistance is connected in parallel to its coil. The remaining pair of the current i.e., (I–Ig) flows through the resistance.
Here, I = Circuit current and Ig = Current through galvanometer
6. A magnetic field that varies in magnitude from point to point but has a constant direction (east to west) is set up in a chamber. A charged particle enters the chamber and travels undeflected along a straight path with constant speed. What can you say about the direction of initial velocity of the particle? [SQP 2013]
7. Show with the help of a diagram, how the force between the two conductors would change when the currents in them flow in the opposite directions. [OD 2015]
Last-Minute Revision Tips for Chapter 4
Before the Physics board exam, follow these strategies:
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Revise all formulas daily (F = qvB sinθ, B for straight conductor and loop).
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Practice direction rules repeatedly.
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Solve previous year board questions.
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Draw neat and labeled diagrams in derivations.
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Focus on important derivations and numericals rather than new topics.
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Practice time-bound problem solving to improve speed.
High-Weightage Derivations to Revise
To improve your score, focus on these derivations:
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Magnetic field due to long straight conductor (Biot–Savart Law).
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Force between two parallel current-carrying conductors.
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Torque on a rectangular current loop.
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Cyclotron frequency derivation.
Clear stepwise presentation in these derivations ensures better marks.