Current Electricity: Class 12 Previous Year Questions

Current Electricity 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. Assertion (A) : Two electric heaters of power P1 and P2 (> P1) are joined in series across a dc source of voltage V. The power consumed by the combination will be less than that consumed by P1 when connected across the same source. 1 Reason (R) : The power con…
   Board 20261 markAssertion-Reason
2. What is the order of magnitude of drift velocity of electrons in a conductor ? Deduce the relation between the current flowing through a conductor and drift velocity of electrons in it.
   Board 20262 marksshort answer
3.  SECTION E 31. (a) An electric dipole consists of two point charges q and –q separated by a distance 2a. Derive an expression for the electric field  E due to this dipole at a point distant r from the centre of the dipole on the equatorial plane. Write the e…
   Board 20265 markslong answer
4. A heating element using nichrome is connected to a 220 V supply. Initially it draws a current of 2.9 A. After some time, the current attains a steady value of 2.5 A. Find the steady temperature of the heating element if the room temperature is 27 C. The tempe…
   Board 20262 marksshort answer
5. A battery of emf E and internal resistance r is connected to a rheostat. When a current of 2A is dawn from the battery, the potential difference across the rheostat is 5V. The potential difference becomes 4V when a current of 4A is drawn from the battery. Calc…
   Board 20252 marksshort answer
6. (a) A cell of e.m.f. E and internal resistance r is connected with a variable external resistance R and a voltmeter showing potential drop Vacross R. Obtain the relationship between V, E, R and r. (b) Draw the shape of the graph showing the variation of termin…
   Board 20253 marksshort answer
7. g p g p q 29. A circuit consisting of a capacitor C, a resistor of resistance R and an ideal battery of emf V, as shown in figure is known as RC series circuit. 4×1=4 As soon as the circuit is completed by closing key S, (keeping S open) charges begin to flow …
   Board 20254 marksshort answer
8. (a) Two batteries of emf's 3V & 6V and internal resistances 0.2 Q & 0.4 are connected in parallel. This combination is connected to a 4 2 resistor. Find : (i) the equivalent emf of the combination (ii) the equivalent internal resistance of the combination (i) …
   Board 20253 marksshort answer
9. Two wires P and Q are made of the same material. The wire Q has twice the diameter and half the length as that of wire P. If the resistance of wire P is R, the resistance of the wire Q will be (A) (B) (C) (D) 2R
   Board 20251 markMCQ
10. A student has three resistors, each of resistance R. To obtain a resistance R, she should connect of (A) allthethree resistorsin series. (B) all the three resistors in parallel. (C) two resistors in series and then this combination in parallel with the third r…
    Board 20251 markMCQ
11. nXmW© GaAs Ho$ {bE dmoëQ>Vm Ho$ gmW Ymam Ho$ {dMaU H$mo Xem©Zo dmbm J«m\$ Amao{IV H$s{OE & Bg J«m\$ na dh joÌ A§{H$V H$s{OE Ohm± : 2 (H$) à{VamoY G$UmË_H$ h¡, VWm (I) Amo_ Ho$ {Z`_ H$m nmbZ hmoVm h¡ &
    Board 20242 marksshort answer
12. Define resistivity of a conductor. How does the resistivity of a conductor depend upon the following : 2 (a) Number density of free electrons in the conductor (n) (b) Their relaxation time ( )
    Board 20242 marksshort answer
13. When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the circuit. The electrolyte of the cell also offers some resistance in the path of the current, like the conductor. This resistance offered by the ele…
    Board 20244 marksshort answer
14. O~ H$moB© àH$me H$s {H$aU gKZ _mÜ`_ go {dab _mÜ`_ _| g§MaU H$aVr h¡, Vmo dh O~ AmnVZ H$moU _| d¥{Õ H$aVo h¢, Vmo And{V©V {H$aU $gr {deof AmnVZ H$moU Ho$ {bE And{V©V {H$aU XmoZm| _mÜ`_m| Ho$ AÝVamn¥îR> H$mo R>rH$-R>rH$ ñne© H$aVr h¡ & Bg (i) H«$m§{VH$ H$moU na …
    Board 20244 marksshort answer
15. Electrons drift with speed vd in a conductor with potential difference V across its ends. If V is reduced to 2 V , their drift speed will become : (A) 2 vd (B) vd (C) 2 vd (D) 4 vd
    Board 20241 markMCQ
16. The potential difference across a cell in an open circuit is 8 V. It falls to 4 V when a current of 4 A is drawn from it. The internal resistance of the cell is : (a) 4 (b) 3 (c) 2 (d)
    Board 20231 markMCQ
17. A cell of emf E is connected across an external resistance R. When current ·I' is drawn from the cell, the potential difference across the electrodes of the cell drops to V. The internal resistance 'r' of the cell is E-V E-V (a) (b) (E- V R E-V (c) (d)
    Board 20231 markMCQ
18. A steady current flows through a metallic wire whose area of cross-section (A) increases continuously from one end of the wire to the other. The magnitude of drift velocity (vd) of the free electrons as a (a) (b) (c) (d)
    Board 20231 markMCQ
19. AmaoI _| {H$gr Am`VmH$ma MmbH$ PSRQ H$mo Xem©`m J`m h¡ {Og_| J{V_mZ ^wOm PQ H$m à{VamoY h¡ VWm PSRQ H$m à{VamoY CnojUr` h¡ & O~ PQ H$mo doJ v go J{V H$amB© OmVr h¡ Vmo ào[aV {d.dm. ~b (emf) H$m n[a_mU {ZåZ{b{IV _| go {H$g na {Z^©a H$aVm h¡ ? (a) Mwå~H$s` joÌ (…
    Board 20231 markMCQ
20. Define current density and relaxation time. Derive an expression for resistivity of a conductor in terms of number density of charge carriers in the conductor and relaxation time.
    Board 20233 marksshort answer

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