CBSE Class 12 Physics Magnetic Effects of Electric Current Objective Questions

CBSE Class 12 Physics Magnetic Effects of Electric Current Objective Questions. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

1. Two circular coils P and Q are made from similar wires but radius of Q is twice that of P. What should be the value of potential difference across them so that the magnetic induction at their centre may be the same?
(a) V_q = 2 V_p (b) V_q = 3V_P (c) V_q = 4V_p (d) V_q = 1/4 V_p

2. The radius of the circular path or helical path followed by the test change q0 moving in magnetic field B with velocity v is
(a) mv sin θ / q₀ B  (b) mv cos θ / q₀ B  (c) mv/ q₀ B (d) mv tan θ/q₀ B

3. An electron accelerated through a potential difference V enters into a uniform transverse magnetic field and experiences a force F. If the accelerating potential is increased to 2 V, the electron in the same magnetic field will experience a force :
(a) F (b) F/2 (c) √2 F (d) 2F

4. A charged particle moving in a uniform magnetic field penetrates a layer of lead and loses one half of its kinetic energy. The ratio of radius of curvature to the original radius is
(a) 2 (b) √2 (c) 1/2 (d) 1/ √2

5. Two straight long conductors AOB and COD are perpendicular to each other and carry currents i1 and i2. The magnitude of the magnetic induction at a point P at a distance d from the point O in a direction perpendicular to the plane ABCD is

6. A current of 10 amp. is flowing in a wire of length 1.5 metre. A force of 15 newton acts on it when it is placed in a uniform magnetic field of 2 tesla. The angle between the magnetic field and the direction of current is
(a) 30º (b) 45º (c) 60º (d) 90º

7. A particle carrying a charge equal to 100 times the charge on an electron is rotating per second in a circular path of radius 0.8 m. The value of the magnetic field produced at the centre will be (μ0  permeability constant).
(a) 10^–7/μ0 (b) 10^–17 μ0 (c) 10^–6 / μ0 (d) 10^–7 μ0

8. The magnetic field at the centre O of the circular portion of the current carrying wire of radius 3 cm is
(a) (8π/3) × 10^–5 T (b) (8π/3) × 10^–4 T π/2 (c) 2π × 10^–5 T (d) 2π × 10^–4 T

9. A long wire carries a current of 20 A along the axis of a solenoid. The field due to the solenoid is 4 mT. the resultant field at a point 3 mm from the solenoid axis is
(a) 1.33 m T (b) 4.2 mT (c) 2.1 m T (d) 8.4 m T

10. A circular current carrying coil has a radius R. The distance from the centre of the coil on the axis where the magnetic induction will be (1/8)th of its value at the centre of the coil is
(a) √3R  (b) 2R √3 (c) R / √3 (d) 2R / √3

11. A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, identify wrong statement
(a) E = 0, B = 0 (b) E = 0, B ≠ 0 (c) E ≠ 0, B = 0 (d) E ≠ 0, B≠0

12. An electron is moving in a circle of radius r in a uniform magnetic field B. Suddenly the field is reducedto B/2. The radius of the circle now becomes
(a) r/2 (b) r/4 (c) 2 r (d) 4 r

13. A proton and an α-particle, moving with the same kinetic energy, enters a uniform magnetic field normally. The radii of their circular paths will be in the ratio
(a) 1 : 1 (b) 2 : 1 (c) 1 : 2 (d) 4 : 1

14. A beam of electrons is accelerated through a potential difference V. It is then passed normally through a uniform magnetic field where it moves in a circle of radius r. It would have moved in a circle of radius 2r if it were initially accelerated through a potential difference
(a) √2 V (b) 2V (c) 2 √2 V (d) 4V

15. A proton and an α-particle, accelerated through the same potential difference, enter a region of uniform magnetic field normally. If the radius of the proton orbit is 10 cm then the radius of of the α-orbit is
(a) 10 cm (b) 10 √2 cm (c) 20 cm (d) 5 √2 cm

16. Two particles X and Y having equal charge, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii R₁ and R₂ respectively. The ratio of the mass of X to that of Y is
(a) (R₁ / R₂)^1/2 (b) R₂ / R₁ (c) (R₁ / R₂)² (d) R₁ / R₂

17. A particle of charge +q and mass m moving under the influence of a uniform electric field Ei and a uniform magnetic field B k follows a trajectory from P to Q as shown in the figure. The velocities at P and Q are v i and –2v j. Which of the following statements is incorrect

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