MCQs of Current Electricity

Current Electricity MCQs

MCQs of Current Electricity

Showing 21 to 30 out of 119 Questions

21.

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%

22.

At what temperature would be resistance of a copper conductor be double its resistance at 0ºC ? Given ∝ for copper = 3.9 x 10^-3 ºC^-1

(a)	256.4 ºC
(b)	512.8 ºC
(c)	100 ºC
(d)	256.4 K

23.

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)	$\frac{R}{2}$
(c)	$\frac{101 R}{200}$
(d)	$\frac{201 R}{200}$

24.

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 the conductor = 2 x 10^-6m² and electron density for copper n = 8.5 x 10²⁸m^-3

(a)	2.72 x 10³ s
(b)	2.72 x 10⁴ s
(c)	2.72 s
(d)	2.72 x 10^-4 s

25.

Masses of three wires of copper are in the ratio 5 : 3 : 1 and their lengths are in the ratio of 1 : 3 : 5. The ratio of their electrical resistances are _____

(a)	5 : 3 : 1
(b)	$\sqrt{125}$ : 15 : 1
(c)	1 : 15 : 125
(d)	1 : 3 : 5

26.

Two bulbs of 220 V and 100 W are first connected in series and then in parallel with a 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

27.

Electric current is _____

(a)	scalar quantity.
(b)	vector quantity.
(c)	only number
(d)	derived quantity.

28.

If the length of the wire is made half, its conductance _____

(a)	becomes half
(b)	does not change
(c)	becomes double
(d)	becomes four times

29.

Order of colour in carbon resistor is brown, red, orange and silver respectively so its resistance is _____ Ω.

(a)	12 x 10³ Ω ± 10%
(b)	12 x 10³ Ω ± 5%
(c)	21 x 10³ Ω ± 10%
(d)	21 x 10³ Ω ± 5%

30.

H cal. heat is produced when electric current passes through conductor having resistance R so electric current through conductor = _____ per second.

(a)	$\frac{JH}{R}$
(b)	$\sqrt{\frac{JR}{H}}$
(c)	$\sqrt{\frac{HR}{J}}$
(d)	$\sqrt{\frac{JH}{R}}$

Showing 21 to 30 out of 119 Questions