Electric Charges & Fields: Class 12 Previous Year Questions

Electric Charges & Fields questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. A conducting wire connects two charged metallic spheres A and B of radii r1 and r2 respectively. The distance between the spheres is very large compared to their radii. The ratio of electric fields, (EA/EB) at the surfaces of spheres A and B will be 1 (A) r1 r…
   Board 20261 markMCQ
2. Assertion (A) : All atoms have a net magnetic moment. 1 Reason (R) : A current loop does not always behave as a magnetic dipole.
   Board 20261 markAssertion-Reason
3. The magnetic flux  (in Wb) linked with a coil is related to time t (in s) as  = 5 At2 + Bt – 2C The SI units of A and B are respectively 1 (A) Wbs2, Wbs (B) Wb s–1, Wb (C) Wbs–2, Wbs–1 (D) Wbs–1, Wbs–2
   Board 20261 markMCQ
4. In a region, the electric potential varies as V = 10 – 50x, where V is in volts and x in meters. The electric field in the region is  1 (A) 10 N/C along +x (B) 10 N/C along –x (C) 50 N/C along +x (D) 50 N/C along –x
   Board 20261 markMCQ
5. (a) Using Gauss’s law, deduce an experession for electric field at a point due to a uniformly charged infinite plane thin sheet. 3 (b) Two large thin plane sheets, each having surface charge density  are held close and parallel to each other in air. What is …
   Board 20263 marksshort answer
6. Two metal spheres of radii r1 and r2 (> r1) having charges q1 and q2 respectively kept in air, are brought in contact. Which of the following statements is not correct ? 1 (A) The total charge of the two spheres is conserved. (B) Both spheres attain the same p…
   Board 20261 markMCQ
7. (a) (i) What is the source of force acting on a current-carrying conductor placed in a magnetic field ? Obtain the expression for force acting between two long straight parallel conductors carrying steady currents and hence define 'ampere'. Page 21 of 24 (i) e…
   Board 20255 markscase-based
8. The magnetic field due to a small magnetic dipole of dipole moment M' at a distance 'r' from the centre along the axis of the dipole is given by "o.2M (A) (B) 4··3 4·× o..M 2M (C) (D) 4·× 2r3 4·
   Board 20251 markMCQ
9. Two charges -q each are placed at the vertices A and B of an equilateral triangle ABC. If M is the mid-point of AB, the net electric field at C will point along (A) CA (B) CB (C) MC (D) CM
   Board 20251 markMCQ
10. (i) 31. (a) A small conducting sphere A of radius r charged to a potential V, is enclosed by a spherical conducting shell B of radius R. If A and B are connected by a thin wire, calculate the final potential on sphere A and shell B. (i) Write two characteristi…
    Board 20255 markslong answer
11. (a) In a region of a uniform electric field E, a negatively charged particle is moving with a constant velocity = -vi near a long straight conductor coinciding with Xx' axis and carrying current I towards -X axis. The particle remains at a distance d from the …
    Board 20253 marksshort answer
12. Figure shows variation of Coulomb force (F) acting between two point and (q2, qg). If q2 is positive and least in magnitude, then the magnitudes of qi, q2 and qg are such that (q q2) (q2, 9g) (A) (B) >> > >() >>()
    Board 20251 markvery short
13. Which one of the following statements is correct ? Electric field due to static charges is (A) conservative and field lines do not form closed loops. (B) conservative and field lines form closed loops. (C) non-conservative and field lines do not form closed lo…
    Board 20251 markMCQ
14. (a) (i) Obtain an expression for the electric potential due to a small dipole of dipole moment p , at a point r from its centre, for much larger distances compared to the size of the dipole. (ii) Three point charges q, 2q and nq are placed at the vertices of a…
    Board 20245 markslong answer
15. A thin plastic rod is bent into a circular ring of radius R. It is uniformly charged with charge density . The magnitude of the electric field at its centre is : (A) R 2 0 (B) Zero (C) 0R (D) R 4 0
    Board 20241 markMCQ
16. Two charged particles P and Q, having the same charge but different masses mP and mQ, start from rest and travel equal distances in a uniform electric field E in time tP and tQ respectively. Neglecting the effect of gravity, the ratio Q P t t is : (A) Q P m m …
    Board 20241 markMCQ
17. Which of the following quantity/quantities remains same in primary and secondary coils of an ideal transformer ? Current, Voltage, Power, Magnetic flux (A) Current only (B) Voltage only (C) Power only (D) Magnetic flux and Power both
    Board 20241 markMCQ
18. (a) Two charged conducting spheres of radii a and b are connected to each other by a wire. Find the ratio of the electric fields at their surfaces. OR (b) A parallel plate capacitor (A) of capacitance C is charged by a battery to voltage V. The battery is disc…
    Board 20233 marksshort answer
19. (i) (a) Use Gauss' law to obtain an expression for the electric field due to an infinitely long thin straight wire with uniform linear charge density 2. (ii) An infinitely long positively charged straight wire has a linear charge density 2. An electron is revo…
    Board 20235 markscase-based
20. Assertion (A) : Work done in moving a charge around a closed path, in an electric field is always zero. Reason (R) : Electrostatic force is a conservative force.
    Board 20231 markAssertion-Reason

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