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)
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 specific resistance of all metals is most affected by :
(1) Temperature
(2) Pressure
(3) Degree of illumination
(4) Applied magnetic field
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
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
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
Which of the following has a negative temperature coefficient of resistance?
(1) C
(2) Fe
(3) Mn
(4) Ag