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 temperature coefficient of resistance for a wire is 0.00125/°C. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is
(1) 1154 K
(2) 1100 K
(3) 1400 K
(4) 1127 K
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
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
If 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\(\sqrt{\mathrm{T}} \) |
3. | zero. | 4. | finite but independent of temperature. |
The specific resistance of all metals is most affected by :
(1) Temperature
(2) Pressure
(3) Degree of illumination
(4) Applied magnetic field