If negligibly small current is passed though a wire of length 15 m & resistance of 5Ω, having uniform cross section of 6 × 10^–7 m², then coefficient of resistivity of material is

1×10^–7Ω–m
2×10–7Ω^–7–m
3×10^–7Ω–m
4×10^–7 Ω–m

Solution

(Hint ⇒ ρ = ^R.A⁄_l = Coefficient of resistivity)

If the resistance of a conductor is 5Ω at 50º C & 7Ω at 100º C, then mean temperature coefficient of resistance(of material) is

0.013/ ºC
0.004/ ºC
0.006/ ºC
0.008/ ºC

Solution

Two identical cells connected in series send 1.0 A current through a 5 Ω resistor. When they are connected in parallel,they send 0.8 A current through the same resistor. What is the internal resistance of the cell?

0.5 Ω
1.0 Ω
1.5 Ω
2.5 Ω

Solution

2, 4 and 6 S are conductances of three conductors. When they are joined in parallel, their equivalent conductance will be

12 S
(1/12) S
(12/11) S
(11/12) S

Solution

2, 4 and 6 S are the conductances of three conductors.When they are joined in series, their equivalent conductance will be

12 S
(1/12) S
(12/11) S
(11/12) S

Solution

A wire X is half the diameter and half the length of a wire Y of similar material. The ratio of r esistance of X to that of Y is

8 : 1
4 : 1
2 : 1
1 : 1

Solution

The amount of charge Q passed in time t through a cross-section of a wire is Q = 5 t² + 3 t +1.The value of current at time t = 5 s is

9 A
49 A
53 A
None of these

Solution

I = ^dQ⁄_dt = 10t + 3

At t = 5s, I= 10 ×5 + 3 = 53 A

A capacitor of 10μF has a pot. difference of 40 volts across it. If it is discharged in 0.2 second, the average current during discharge is

2 m A
4 m A
1 m A
0.5 m A

Solution

In a neon gas discharge tube Ne+ ions moving through across-section of the tube each second to the right is 2.9 ×10¹⁸, while 1.2 × 10¹⁸ electrons move towards left in the same time; the electronic charge being 1.6 × 10–19 C,then etelectric current is

0.27 A to the right
0.66 A to the right
0.66 A to the left
zero

Solution

Current,I =(2.9 × 10¹⁸ + 1.2 × 10¹⁸) × 1.6 × 10^–19 towards right.

Two identical fuses are rated at 10 A. If they are joined

(A)in parallel, the combination acts as a fuse of rating 20 A

(B)in parallel, the combination acts as a fuse of rating 5 A

(C)in series, the combination acts as a fuse of rating 10 A

(D)in series, the combination acts as a fuse of rating 20 A Select the correct options.

A, B
A, C
B, D
B, C, D

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