A silver wire has a resistance of \(2.1~\Omega\) at \(27.5^\circ \text{C},\) and a resistance of \(2.7~\Omega\) at \(100^\circ \text{C}.\) The temperature coefficient of resistivity of silver is:
1. \(0.0033^\circ \text{C}^{-1}\)
2. \(0.039^\circ \text{C}^{-1}\)
3. \(0.0039^\circ \text{C}^{-1}\)
4. \(0.033^\circ \text{C}^{-1}\)

The current drawn from a \(12~\text{V}\) supply with internal resistance \(0.5~\Omega\) by the infinite network (shown in the figure) is:

    
1. \(3.12~\text{A}\)
2. \(3.72~\text{A}\)
3. \(2.29~\text{A}\)
4. \(2.37~\text{A}\)

Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Ω maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents up to a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 kΩ is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf ε and the balance point found similarly, turns out to be at 82.3 cm length of the wire. The value of ε is:

1. 1.33 V
2. 1.50 V
3. 1.24 V
4. 1.07 V

Figure shows a potentiometer circuit for comparison of two resistances. The balance point with a standard resistor R=10.0 Ω is found to be 58.3 cm, while that with the unknown resistance X is 68.5 cm. The value of X is:

1. $12.1\Omega$

2. $12.4 \Omega$

3. $10.3 \Omega$

4. $11.7 \Omega$

The figure shows a 2.0 V potentiometer used for the determination of the internal resistance of a 1.5 V cell. The balance point of the cell in the open circuit is 76.3 cm. When a resistor of 9.5 Ω is used in the external circuit of the cell, the balance point shifts to 64.8 cm length of the potentiometer wire. The internal resistance of the cell is:
    
1. \(1.68~\Omega \)
2. \(0.13~\Omega \)
3. \(0.31~\Omega \)
4. \(1.12~\Omega \)

A potential difference of 10 V is applied across a conductor of $1000 \mathrm{\Omega }$. The number of electrons flowing through the conductor in 300 sec is:

1. $1.875\times {10}^{16}$

2. $1.875\times {10}^{17}$

3. $1.875\times {10}^{22}$

4. $1.875\times {10}^{19}$

Ohm's law fails in:

1. Diode

2. Thyristor

3. PN junction system

4. All of these

Identical pieces of Ge and Cu are taken and cooled, then:

1. Resistivity of both increases

2. Resistivity of both decreases

3. Resistivity of Cu increases and Ge decreases

4. Resistivity of Cu decreases and Ge increases

A potential difference of 5 V is applied across a conductor of length 10 cm. If the drift velocity of electrons is $2.5\times {10}^{-4}$ m/s, then the electron mobility will be:

1. $5\times {10}^{-4} {\mathrm{m}}^2 {\mathrm{V}}^{-1} {\mathrm{s}}^{-1}$

2. $5\times {10}^{-6} {\mathrm{m}}^2 {\mathrm{V}}^{-1} {\mathrm{s}}^{-1}$

3. $5\times {10}^{-2 }{\mathrm{m}}^2 {\mathrm{V}}^{-1} {\mathrm{s}}^{-1}$

4. Zero

The resistance of a rectangular block of copper of dimensions $2 \mathrm{mm}\times 2 \mathrm{mm}\times 5 \mathrm{m}$ between two square faces is $0.02\mathrm{\Omega }$. What is the resistivity of copper?

1. $1.6\times {10}^{-8} \mathrm{\Omega }$

2. $1.6\times {10}^{-6} \mathrm{\Omega }-\mathrm{m}$

3. $1.6\times {10}^{-8} \mathrm{\Omega }-\mathrm{m}$

4. Zero