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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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) R4

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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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

Concept Questions :-

Derivation of Ohm's law
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Difficulty Level: