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

(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
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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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The resistance of a wire is R. If the length of the wire is doubled by stretching, then the new resistance will be

(1) 2R

(2) 4R

(3) R

(4) $\frac{R}{4}$

Concept Questions :-

Derivation of Ohm's law
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Which of the following has a negative temperature coefficient

(1) C

(2) Fe

(3) Mn

(4) Ag

Concept Questions :-

Derivation of Ohm's law
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The reciprocal of resistance is :

(1) Conductance

(2) Resistivity

(3) Voltage

(4) None of the above

Concept Questions :-

Derivation of Ohm's law
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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

Concept Questions :-

Derivation of Ohm's law
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Difficulty Level: