The resistance of platinum wire at 0 is 22.05 and at 100 it becomes 22.70 . When the wire is heated to a temperature of t the resistance of wire becomes 24.91. The value of t is
1. 220
2. 440
3. 310
4. 550
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 |
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.
The specific resistance of all metals is most affected by :
1. Temperature
2. Pressure
3. Degree of illumination
4. Applied magnetic field