The resistivity of iron is 1 × 10–7 ohm – m. The resistance of iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in ohm – m will be :
(1) 1 × 10–7
(2) 2 × 10–7
(3) 4 × 10–7
(4) 8 × 10–7
The resistivity of a wire :
1. | Increases with the length of the wire |
2. | Decreases with the area of cross-section |
3. | Decreases with the length and increases with the cross-section of the wire |
4. | None of the above statement is correct |
Drift velocity vd varies with the intensity of electric field as per the relation:
1.
2.
3. vd = constant
4.
In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be :
(1) 4 volts
(2) 4 amperes
(3) 2 amperes
(4) 2 volts
The specific resistance of a wire is ρ, its volume is 3 m3 and its resistance is 3 ohms, then its length will be
(1)
(2)
(3)
(4)
When a piece of aluminum wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become :
(1) Two times
(2) Four times
(3) Eight times
(4) Sixteen times
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)
(2)
(3)
(4)