The positive temperature coefficient of resistance is for :
1. Carbon
2. Germanium
3. Copper
4. An electrolyte
The electric intensity E, current density j and specific resistance k are related to each other by the relation :
1. E = j/k
2. E = jk
3. E = k/j
4. k = jE
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 \(n\), \(e\), \(\tau\) 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. \(\frac{ml}{ne^2\tau A}\)
2. \(\frac{m\tau^2A}{ne^2l}\)
3. \(\frac{ne^2\tau A}{2ml}\)
4. \(\frac{ne^2 A}{2m\tau l}\)
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
Which of the following has a negative temperature coefficient of resistance?
1. C
2. Fe
3. Mn
4. Ag
The reciprocal of resistance is :
1. Conductance
2. Resistivity
3. Voltage
4. None of the above
A solenoid is at the potential difference of \(60~\text V\) and the current flows through it is \(15~\text A\) then the resistance of the coil will be:
1. \(4~\Omega\)
2. \(8~\Omega\)
3. \(0.25~\Omega\)
4. \(2~\Omega\)