MCQs of Current Electricity

Current Electricity MCQs

MCQs of Current Electricity

Showing 81 to 90 out of 119 Questions

81.

Internal resistance of a cell of emf 4 V is 0·1 Ω, and 3·9 Ω resistor is connected across it. Voltage across the cell is _____.

(a)	3·8 V
(b)	0·1 V
(c)	2 V
(d)	3·9 V

82.

Area of cross-section of a copper wire is equal to the area of a square of 2 mm length. It carries a current of 8 A. Find drift velocity of electrons.(Density of three electrons in copper is 8 ×10²⁸ m^-3)

(a)	1·56 × 10^-2 m^-1
(b)	1·56 × 10^-4 m^-1
(c)	3·12 × 10^-2 m^-1
(d)	1·56 × 10^-3 m^-1

83.

The physical quantity having the dimensions [M^-1L^-3T³A²] is _____.

(a)	resistance
(b)	resistivity
(c)	electrical conductivity
(d)	electromotive force

84.

Length of a wire is halved keeping its cross-section constant. What will be its new conductance ?

(a)	Halved
(b)	Does not change
(c)	Doubled
(d)	Four times

85.

A wire of resistance 20 Ω is bent from the middle by 180º and then both parts are twisted. What will be its new resistance ?

(a)	20 Ω
(b)	10 Ω
(c)	5 Ω
(d)	4 Ω

86.

At 100ºC resistance of a conducting coil is 4·2 Ω. If temperature coefficient of resistance is 0·004 (ºC)^-1, what will be its resistance at 0º C ?

(a)	5 Ω
(b)	3 Ω
(c)	4 Ω
(d)	3·5 Ω

87.

emf is a kind of

(a)	non-electrical force
(b)	energy
(c)	electrical force
(d)	electromagnetic force

88.

Two wires of same dimensions but resistivities

p_{1}

and

p_{2}

are connected in series. The equivalent resistivity of the combination is _____.

(a)	$\sqrt{p_{1} p_{2}}$
(b)	$(p_{1} + p_{2})$
(c)	$\frac{p_{1} + p_{2}}{2}$
(d)	None of the above

89.

Resistivity of copper is 1·72 × 10^-8 Ω m and current density through a copper wire is 1·3 × 10⁵ A/m². Find the electric field set up in the wire

(a)	2·2 × 10^-3 V/m
(b)	1·1 × 10^-3 V/m
(c)	2·2 × 10^-6 V/m
(d)	1·1 × 10³ V/m

90.

Suppose drift velocity over the entire cross section of a wire is

v (r) = v_{0} [1 - \frac{r}{R}]

. What is the current density at the surface of the wire ?

(a)	Zero
(b)	$v_{0} R$
(c)	$n e v_{0}$
(d)	$n e v \frac{r}{R}$

Showing 81 to 90 out of 119 Questions