MCQs of Current Electricity

Showing 11 to 20 out of 119 Questions
11.
Masses of three wires of copper are in the ratio 5 : 3 : 1 and their lengths are in the ratio 1 : 3 : 5. The ratio of their electrical resistances are _____.
 (a) 5 : 3 : 1 (b) (c) 1 : 15 : 125 (d) 1 : 3 : 5
12.
The resistance of a 10 m long potentiometer wire is 20 Ω. It is connected in series with a 3 V battery and 10 Ω resistor. The potential difference between two points separated by distance 30 cm is equal to _____ .
 (a) 0.02 V (b) 0.06 V (c) 0.1 V (d) 1.2 V
13.
n identical cells each of emf ε and internal resistance r are connected in parallel with resistor R. The current flowing through resistor R is, _____ .
 (a) $\frac{n\epsilon }{\mathrm{R}+nr}$ (b) $\frac{n\epsilon }{\mathrm{nR}+r}$ (c) $\frac{\epsilon }{\mathrm{R}+r}$ (d) $\frac{\epsilon }{\mathrm{nR}+r}$
14.
 (a) (b) (c) (d) n times
15.
If the current in an electric bulb increases by 1 %, what will be the change in the power of a bulb ? [Assume that the resistance of the filament of a bulb remains constant.]
 (a) increases by 1 % (b) decreases by 1 % (c) increases by 2 % (d) decreases by 2 %
16.
Two bulbs of 220 V and 100 W are first connected in series and than in parallel with supply of 220 V. Total power in both the cases will be _____ .
 (a) 50 W, 100 W (b) 100 W, 50 W (c) 200 W, 150 W (d) 50 W, 200 W
17.
In a hydrogen atom, the electron is moving in a circular orbit of radius 5.3 x 10-11 m with a constant speed of 2.2 x 106 ms-1. The electric current formed due to the motion of electron is _____
 (a) 1.12 A (b) 1.06 mA (c) 1.06 A (d) 1.12 mA
18.
A ring of radius R and linear charge density λ on its surface is performing rotational motion about an axis perpendicular to its plane. If the angular velocity of the ring is ω, how much current is constituted by the ring ?
 (a) Rωλ (b) R2ωλ (c) Rω2λ (d) Rωλ2
19.
A cell supplies a current of 0.9 A through a 2 Ω resistor and current of 0.3 A through a 7 Ω resistor. What is the internal resistance of the cell ?
 (a) 0.5 Ω (b) 1.0 Ω (c) 1.2 Ω (d) 2.0 Ω
20.
A current density of 2.5 Am-2 is found to exist in a conductor when an electric field of 5 x 10-8 Vm-1 is applied across it. The resistivity of a conductor is _____
 (a) 1 x 10-8 Ωm (b) 2 x 10-8 Ωm (c) 0.5 x 10-8 Ωm (d) 12.5 x 10-8 Ωm
Showing 11 to 20 out of 119 Questions