Through a semiconductor, an electric current is due to drift off:

(1) Free electrons

(2) Free electrons and holes

(3) Positive and negative ions

(4) Protons

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

A metallic block has no potential difference applied across it, then the mean velocity of free electron is (T = absolute temperature of the block) :

(1) Proportional to T

(2) Proportional to $\sqrt{T}$

(3) Zero

(4) Finite but independent of temperature

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The specific resistance of all metals is most affected by :

(1) Temperature

(2) Pressure

(3) Degree of illumination

(4) Applied magnetic field

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The positive temperature coefficient of resistance is for :

(1) Carbon

(2) Germanium

(3) Copper

(4) An electrolyte

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Derivation of Ohm's law
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Derivation of Ohm's law
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Derivation of Ohm's law
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Current and current density
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

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

Concept Questions :-

Current and current density