The electric intensity E, current density j and specific resistance k are related to each other by the relation :

(1) E = j/k

(2) E = jk

(3) E = k/j

(4) k = jE

The resistance of a wire of uniform diameter d and length L is R. The resistance of another wire of the same material but diameter 2d and length 4L will be :

(1) 2R

(2) R

(3) R/2

(4) R/4

There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1 mm². If the number of free electrons per cm³ is 8.4 × 10²², then the drift velocity would be :

1. 1.0 mm/sec

2. 1.0 m/sec

3. 0.1 mm/sec

4. 0.01 mm/sec

An electric wire of length ‘I’ and area of cross-section a has a resistance R ohms. Another wire of the same material having the same length and area of cross-section 4a has a resistance of :

(1) 4R

(2) R/4

(3) R/16

(4) 16R

If n, e, τ and m respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length l and area of cross-section A will be 

(1) $\frac{ml}{n{e}^2\tau A}$

(2) $\frac{m{\tau }^{2}A}{n{e}^{2}l}$

(3) $\frac{n{e}^2\tau A}{2ml}$

(4) $\frac{n{e}^{2}A}{2m\tau l}$ 

The relaxation time in conductors :

(1) Increases with the increase in temperature

(2) Decreases with the increase in temperature

(3) It does not depend on the temperature

(4) All of the sudden changes at 400 K

Which of the following has a negative temperature coefficient of resistance?

(1) C

(2) Fe

(3) Mn

(4) Ag

The reciprocal of resistance is :

(1) Conductance

(2) Resistivity

(3) Voltage

(4) None of the above

A solenoid is at the potential difference 60 V and current flows through it is 15 ampere, then the resistance of coil will be :

(1) 4 Ω

(2) 8 Ω

(3) 0.25 Ω

(4) 2 Ω

All of the following statements are true except 

(1) Conductance is the reciprocal of resistance and is measured in Siemens

(2) Ohm's law is not applicable at very low and very high temperatures

(3) Ohm's law is applicable to semiconductors

(4) Ohm's law is not applicable to electron tubes, discharge tubes and electrolytes