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
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The positive temperature coefficient of resistance is for :

(1) Carbon

(2) Germanium

(3) Copper

(4) An electrolyte

Concept Questions :-

Current and current density
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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
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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
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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
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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
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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) mlne2τA

(2) mτ2Ane2l

(3) ne2τA2ml

(4) ne2A2mτl 

Concept Questions :-

Current and current density
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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
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The resistance of a wire is 10 Ω. Its length is increased by 10% by stretching. The new resistance will now be :

(1) 12 Ω

(2) 1.2 Ω

(3) 13 Ω

(4) 11 Ω

Concept Questions :-

Derivation of Ohm's law
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Resistance of tungsten wire at 150°C is 133 Ω. Its resistance temperature coefficient is 0.0045/°C. The resistance of this wire at 500°C will be 

(1) 180 Ω

(2) 225 Ω

(3) 258 Ω

(4) 317 Ω

Concept Questions :-

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

Difficulty Level: