Moving Charges and Magnetism

33 solved questions from Class 12 Physics, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the fundamental law or governing principle of 'Moving Charges and Magnetism' in Class 12 Physics? medium MCQ Fundamental Physical Law
• 2 What is the SI unit and dimensional formula for the key physical quantity studied in 'Moving Charges and Magnetism'? medium MCQ SI Units & Dimensional Analysis
• 3 How does the field or potential intensity vary with distance r in 'Moving Charges and Magnetism'? medium MCQ Spatial Distance Dependence
• 4 What is the net flux or circulation integral through a closed surface in 'Moving Charges and Magnetism'? medium MCQ Gauss's Theorem & Boundary Integrals
• 5 Why do field lines in 'Moving Charges and Magnetism' never intersect each other? medium MCQ Field Line Properties
• 6 An electron enters a uniform magnetic field of magnitude 0.20 T perpendicular to its velocity. Its speed is 2.0×10^6 m s^-1. Find the radius of its circular path (in meters). medium 2 marks Radius of charge in magnetic field
• 7 An air‑core circular coil of radius 0.10 m carries a current I = 20 A in the clockwise direction when viewed from above. What is the magnitude of the magnetic field at the centre of the coil? easy MCQ 1 mark Magnetic field of a current loop
• 8 Consider a rectangular current loop ABCD placed in a uniform magnetic field B = 0.5 T k (out of the page). The sides AB and CD are each 6 cm long, and the sides BC and DA are each 4 cm long. A current I = 3 A flows clockwise when viewed from above. The plane of the loop makes an angle θ = 30° with the direction of B (the angle is between the normal to the loop and B). hard 3 marks Torque on a current loop
• 9 A long solenoid has 1200 turns per metre and carries a current of 2.5 A. Find the magnitude of the magnetic field inside the solenoid (in tesla). medium 2 marks Magnetic field inside a solenoid
• 10 Two long, parallel conductors are 5.0 cm apart. Each carries a current I = 6.0 A in the same direction. (a) Find the magnitude of the magnetic field at a point 2.0 cm from the first conductor. (b) Determine the magnetic force per unit length exerted on the second conductor by the first. medium 3 marks Magnetic field of straight wire and force between wires
• 11 A circular air‑core coil of radius r = 5.0 cm has N = 200 turns and carries a current I = 3.0 A clockwise when viewed from above. What is the magnitude of the magnetic field at the centre of the coil? easy MCQ 1 mark Magnetic field of a circular coil
• 12 An electron enters a uniform magnetic field of magnitude B = 0.30 T with speed v = 1.5×10^6 m s^-1 at an angle of 45° to the field direction. Find the radius of the circular component of its trajectory. medium 2 marks Radius of charged particle in magnetic field
• 13 A rectangular current loop ABCD of width w = 5.0 cm and length l = 12.0 cm carries a current I = 4.0 A clockwise when viewed from above. The loop lies in a uniform magnetic field B = 0.8 T k (out of the page). The normal to the plane of the loop makes an angle θ = 40° with B. (a) Find the magnitude and direction of the torque acting on the loop. (b) Calculate the magnetic potential energy of the loop in this orientation. (c) If the loop is rotated slowly to align its normal with B, how much work is done by the magnetic field? hard 5 marks Torque and energy of a current loop in magnetic field
• 14 Two long, straight conductors are placed d = 8.0 cm apart. Currents I_1 = 3.0 A and I_2 = 4.0 A flow in opposite directions. What is the magnitude of the force per unit length on each conductor? medium MCQ 3 marks Force between parallel current-carrying conductors
• 15 A solenoid of length L = 0.50 m has N = 500 tightly wound turns and carries a current I = 2.0 A. Find the magnitude of the magnetic field at any point inside the solenoid. easy 2 marks Magnetic field inside a solenoid
• 16 A proton of speed v = 2.0×10^6 m s^-1 enters a uniform magnetic field B = 0.20 T at an angle θ = 30° to the field direction. Find the radius of the circular component of its helical trajectory. hard 4 marks Radius of motion of a charged particle in a magnetic field
• 17 A rectangular current loop has length 0.09,m, width 0.04,m and carries a current of 6.0,A. It is placed in a uniform magnetic field of magnitude 0.50,T making an angle of 60° between its normal and the field direction. Find the magnitude of the torque acting on the loop. hard 4 marks Torque on current loop in magnetic field
• 18 A circular current loop of radius 0.08,m has 300 turns and carries a steady current of 2.0,A. Find the magnitude of the magnetic field at the centre of the loop. easy 2 marks Magnetic field of a circular loop
• 19 Two long, straight conductors are separated by a distance of 4.0,cm. The currents in them are 10,A and 5,A, flowing in opposite directions. What is the magnitude of the force per unit length on each conductor? medium 3 marks Force between parallel currents
• 20 A proton of speed 3.0×10^6,m/s enters a uniform magnetic field of magnitude 0.15,T at an angle of 45° to the field direction. Find the radius of the circular component of its helical trajectory. medium 3 marks Radius of charged particle in magnetic field
• 21 A straight conductor of length 0.25,m carries a current of 4,A in a uniform magnetic field of magnitude 0.5,T perpendicular to the conductor. Find the magnitude of the magnetic force on the conductor. easy 1 mark Lorentz force on straight conductor
• 22 A rectangular current loop of length 0.12,m and width 0.05,m carries a current of 5,A. It is placed in a uniform magnetic field of magnitude 0.8,T. The normal to the plane of the loop makes an angle of 30° with the direction of the magnetic field. Find the magnitude of the torque acting on the loop and specify its direction. hard 3 marks torque on current loop in magnetic field
• 23 Two long parallel conductors are separated by a distance of 5,cm. Each carries a current of 8,A in the same direction. What is the force per unit length on each conductor? medium 2 marks force between parallel currents
• 24 A proton with speed 2.5×10^6,m/s enters a uniform magnetic field of magnitude 0.25,T making an angle of 70° with the field direction. Find the radius of the circular component of its helical path. hard 4 marks radius of helical motion in magnetic field
• 25 A 2.0 × 10⁶ m s⁻¹ moving electron enters a uniform magnetic field of 0.5 T perpendicular to its velocity. What is the magnitude of the magnetic force on the electron? easy MCQ 2 marks Magnetic force on a moving charge
• 26 A proton with a speed of 4.0×10^6 m/s enters a uniform magnetic field of 0.4 T at an angle of 60^circ to the field direction. What is the radius of the circular component of its helical trajectory? hard 5 marks Helical motion of a charged particle in a magnetic field
• 27 Two long parallel conductors are separated by a distance of 0.07 m. The currents are I_1 = 12,A and I_2 = 5,A, flowing in opposite directions. What is the magnitude of the force per unit length exerted on each conductor? medium 3 marks Force between parallel currents
• 28 A rectangular current loop of length 0.15,m and width 0.08,m carries a current of 4,A counter‑clockwise when viewed from above. It is placed in a uniform magnetic field of 0.3,T making an angle of 25^circ between the normal to the loop and the field direction. What is the magnitude of the torque on the loop and in which direction does it act? hard 4 marks Torque on a current loop
• 29 A charge of +1.2×10^-6,C moves with a speed of 1.5×10^5,m/s perpendicular to a uniform magnetic field of magnitude 0.25,T. What is the magnitude of the magnetic force acting on the charge? easy 1 mark Magnetic force on a moving charge
• 30 A proton of charge +e and mass 1.67×10^-27,kg moves with speed 4.0×10^6,m/s making an angle of 70° with a uniform magnetic field of magnitude 0.15,T. What is the radius of the circular component of its helical trajectory? hard 3 marks Helical trajectory radius for moving charge
• 31 A rectangular loop with length 0.12,m, width 0.08,m carries a current of 4,A. It is placed in a uniform magnetic field of magnitude 0.35,T directed along the +x‑axis, and the loop’s normal makes an angle of 30° with the field. What is the magnitude of the torque acting on the loop? medium 2 marks Torque on a current loop
• 32 Two long, straight conductors are separated by a distance of 0.04,m. One carries a current of 9,A and the other 7,A, both flowing in opposite directions. What is the magnitude of the force per unit length exerted on each conductor? medium 2 marks Magnetic force between parallel currents
• 33 A particle with charge +2.5×10^-6,C moves with a speed of 2.0×10^5,m/s at an angle of 30° to a uniform magnetic field of magnitude 0.15,T. What is the magnitude of the magnetic force on the particle? easy 1 mark Magnetic force on moving charge