MCQ-CH-3-CURRENT ELECTRICITY
1.A potential difference V is applied across the ends of a conductor. If the length of the conductor is
tripled by stretching it, keeping V constant then which is not correct?
(a) drift velocity of electrons will decrease
(b) resistance of wire will be 9 times
(c) resistivity will be three times
(d) current in conductor will decrease to one ninth times.
2. A wire has a resistance of 16 ohms. It is melted and a new wire is stretched whose diameter is
doubled .What will be the resistance of new wire ?
(a) 1 Ω (b) 6 Ω (c) 1/6 Ω (d) 3 Ω
3. A wire of uniformly stretched by 10%, calculate the percentage change in its
resistance.
(a) 21% (b) 44% (c) 2.1% (d) 4.4%
4. Resistance of a copper coil is 4.6 at 40°C and 5.6 at 100°C. Its resistance at 0°C is:
(a) 4.1 (b) 5.12 (c) 0.96 (d) 4
5. V-I graph for a conductor (platinum wire) at temperatures T1 and T2 is as shown in figure.
In figure (T2-T1) is proportional to:
(a) Cos 2θ (b) sin2θ (c) cot2θ (d) tan2θ
6. A constant voltage is applied between the two ends of a uniform metallic wire. Some heat
whose :
(a) both length and radius are halved
(b) both length and radius are doubled
(c) radius is doubled
(d) length is doubled
7. Three bulbs B1, B2 and B3 of equal resistances are connected to an electric mains as
shown in figure. If the bulb B3 is removed from the circuit then what will be the effect on
the brightness of bulbs B1 and B2 ?
(a) no effect on brightness of B1 and B2
(b) brightness of B1 will increase and B2 will decrease
(c) brightness of B1 will decrease and B2 will increase
(d) brightness of both will increase
8. Three equal resistors connected in series across a source of e.m.f. together dissipated
10W of power, what would be the power dissipated if the same resistors are connected
in parallel across the same source of e.m.f.
(a) 90W (b) 100 W (c) 60 W (D) 30W
9. If each resistor has a value of 10 , find equivalent resistance between points A and B:
(a) 10 (b) 20 (c) 30 (d) 40
10. What are the values of current drawn from the battery and current in 2 Ω resistor in
following circuit:
(a) 1A, 2A (b) 1A, 1A (c) 3A, 1.5A (d) 1.5A, 0.5 A
11. A wire of uniform cross section and length ℓ has a resistance of 16. It is cut into four
equal parts. Each part is stretched uniformly to length ℓ and all the four stretched parts are
connected in parallel. Calculate the total resistance of the combination so formed.
(a) 8 (b) 16 (c) 1 (d) 32
12 cells each of emf 1.5V and internal resistance o.5 Ω are arranged in ‘m’ rows each
contains ‘n’ cells connected in series. Calculate the value of ‘n’ and ‘m’ for which this
combination would send the maximum current through external resistance of 1.5 Ω
(a) n=6, m=2 (b) n=6 , m=2 (c) n=4 , m= 3 (d) n=3 , m= 4
13. Find the value of currents I1, I2, and I3 in the network given below.
(a) I1= 48/11A, I2=-6/11 A, I3= 42/11A
(b) I1= 42/11A, I2=-6/11 A, I3= 48/11A
(c) I1= -6/11A, I2=48/11 A, I3= 42/11A
(d) I1= -6/11A, I2=42/11 A, I3= 48/11A
14. In the given circuit, assuming potential at point A to be zero, the potential at point B is:
(a) zero (b) 1V (c) 2V (d) -2 V
15. Using Kirchhoff’s laws, find the potential difference between points B and D?.
(a) 2/13 volt (b) 1/13 volt (c) zero (d) 2/11 volt
16. In following Wheatstone bridge, if the galvanometer shows zero deflection, then the value
of unknown resistance x is:
(a) 2Ω (b) 4 Ω (c) 5 Ω (d) 2.5 Ω
17. Calculate the equivalent resistance across AB if each resistor is R. If a supply of emf (E)
is connected across points A and B, compute the current through arm AB.
(a) R (b) R/2 (c) R/4 (d) 4R
18. Find out the potential difference between points A and B.
(a) 8V (b) 9V (c) 3V (d) 12 V
19. In the circuit given below the cell E1 and E2 have e.m.fs. of 4V and 8V and internal
resistance of 0.5 and 1 respectively. The terminal potential difference across E1
and E2 respectively are:
(a) 7.5V , 4.25 V (b) 4.25V, 7.5V (c) 7.5V, 4.5V (d) 4.5V, 7.5V
20. In the circuit diagram shown here what should be the value of R so that there is no current
in the branch containing 6V battery ?
(a) 6Ω (b) 2Ω (c) 18 Ω (d) 12 Ω
ANSWER KEY:
1 (c) , 2(a), 3(a), 4(a), 5(c), 6(b), 7(c), 8(a), 9(c), 10(d), 11(b), 12(a), 13(a), 14(c), 15(a), 16(a),
17(b), 18(b), 19(b), 20(d)
