### MCQs of Current Electricity

Showing 1 to 10 out of 119 Questions
1.
In a hydrogen atom, the electron is moving in a circular orbit of radius 5.3 × 10-11 m with a constant speed of 2.2 × 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
2.
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
3.
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 resistance of the cell ?
 (a) 0.5 Ω (b) 1.0 Ω (c) 1.2 Ω (d) 2.0 Ω
4.
A current density of 2.5 Am-2 is found to exist in a conductor when an electric field of 5 × 10-8 Vm-1 is applied across it. The resistance of a conductor is _____ .
 (a) 1 × 10-8 Ωm (b) 2 × 10-8 Ωm (c) 0.5 × 10-8 Ωm (d) 12.5 × 10-8 Ωm
5.
A resistive wire is stretched till its length is increased by 100%. Due to the consequent decrease in diameter, the change in the, resistance of a stretched wire will be _____ .
 (a) 300 % (b) 200 % (c) 100 % (d) 50 %
6.
At what temperature would the resistance of a copper conductor be double its resistance at 0ºC ? Given α for copper =3.9 × 10-3 ºC-1
 (a) 256.4ºC (b) 512.8ºC (c) 100ºC (d) 256.4 K
7.
You are given n identical resistors each of resistance rΩ. First they are connected in such a way that the possible minimum value of resistance is obtained. Then they are connected in a way to get maximum possible resistance. The ratio of minimum and maximum resistance obtained in these way is _____ .
 (a) $\frac{1}{\mathrm{n}}$ (b) n (c) ${\mathrm{n}}^{2}$ (d) $\frac{1}{{\mathrm{n}}^{2}}$
8.
P and Q are two points on a uniform ring of resistance R. O is the centre of the ring. If the part PQ of the ring subtends an angle θ at the centre O of the ring , the equivalent resistance of the ring between the points P and Q will be _____ . [radius of the ring = r and resistance per unit length of the ring = ρ]
 (a) (b) (c) $\frac{\mathrm{R\theta }}{2\mathrm{\pi }}$ (d) $\mathrm{R}\left(\frac{2\mathrm{\pi }-\mathrm{\theta }}{4\mathrm{\pi }}\right)$
9.
A uniform conductor of resistance R is cut into 20 equal pieces. Half of them are joined in series and the remaining half of them are connected in parallel. If the two combinations are joined in series, the effective resistance of all the pieces is :
 (a) R (b) $\frac{\mathrm{R}}{2}$ (c) $\frac{101\mathrm{R}}{200}$ (d) $\frac{201\mathrm{R}}{200}$
10.
What will be the time taken by electron to move with drift velocity from one end to the other end of copper conductor 3 metre long and carrying a current of 3 A ? [The cross-sectional area of conductor =2  × 10-6 m2 and electron density for copper n = 8.5 × 1028 m-3]
 (a) 2.72 × 103s (b) 2.72 × 104s (c) 2.72s (d) 2.72 × 10-4s
Showing 1 to 10 out of 119 Questions