# The number density of free electrons in a copper conductor is 8.5×1028 m–3. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of the cross-section of the wire is 2.0×10–6 m2 and it is carrying a current of 3.0 A. 1.$$2.7 \times10^{4}$$ s 2.$$3.3 \times10^{4}$$ s 3.$$2.0 \times10^{3}$$ s 4.$$3.9 \times10^{3}$$ s

Subtopic:  Current & Current Density |
62%
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Six lead-acid type of secondary cells each of emf $$2.0$$ V and internal resistance $$0.015~\Omega$$ are joined in series to provide a supply to a resistance of $$8.5~\Omega$$. What is the current drawn from the supply?
1. $$2.10~\text{A}$$
2. $$1.39~\text{A}$$
3. $$1.71~\text{A}$$
4. $$2.21~\text{A}$$

Subtopic:  Grouping of Cells |
80%
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A secondary cell after long use has an emf of $$1.9$$ V and a large internal resistance of $$380~\Omega$$. What maximum current can be drawn from the cell?
1. $$0.05~\text{A}$$
2. $$0.005~\text{A}$$
3. $$5.0~\text{A}$$
4. $$0.5~\text{A}$$

Subtopic:  EMF & Terminal Voltage |
87%
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The storage battery of a car has an EMF of $$12$$ V. If the internal resistance of the battery is $$0.4~\Omega$$, what is the maximum current that can be drawn from the battery?

 1 $$30$$ A 2 $$20$$ A 3 $$10$$ A 4 $$40$$ A
Subtopic:  EMF & Terminal Voltage |
86%
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A battery of emf 10 V and internal resistance  is connected to a resistor. If the current in the circuit is 0.5 A, what is the terminal voltage of the battery when the circuit is closed?

1. 10 V
2. 8.5 V
3. 1.5 V
4. 7.2 V

Subtopic:  EMF & Terminal Voltage |
80%
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Three resistors  are combined in series.  If the combination is connected to a battery of emf 12 V and negligible internal resistance, the potential drop across  resistor is:

1. 2 V
2. 5 V
3. 4 V
4. 6 V

Subtopic:  Combination of Resistors |
78%
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Three resistors  are combined in parallel. If the combination is connected to a battery of emf 20 V and negligible internal resistance, the total current drawn from the battery is:

1. 10 A
2. 17 A
3. 13 A
4. 19 A

Subtopic:  Combination of Resistors |
79%
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At room temperature $$(27~^\circ \text{C})$$ the resistance of a heating element is $$100~\Omega$$. What is the temperature of the element if the resistance is found to be $$117~\Omega$$
(Given that the temperature coefficient of the material of the resistor is
$$1.70\times 10^{-4}~^{\circ}\text{C}^{-1}$$)
1. $$1027~^{\circ}\text{C}$$
2. $$1007~^{\circ}\text{C}$$
3. $$1020~^{\circ}\text{C}$$
4.
$$1127~^{\circ}\text{C}$$

Subtopic:  Heating Effects of Current |
73%
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A negligibly small current is passed through a wire of length $$15~\text{m}$$ and uniform cross-section $$6.0\times10^{-7}$$ m2, and its resistance is measured to be $$5.0~\Omega.$$ What is the resistivity of the material at the temperature of the experiment?

 1 $$1\times 10^{-7}~\Omega\text{m}$$ 2 $$2\times 10^{-7}~\Omega\text{m}$$ 3 $$3\times 10^{-7}~\Omega\text{m}$$ 4 $$1.6\times 10^{-7}~\Omega\text{m}$$
Subtopic:  Derivation of Ohm's Law |
87%
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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. $$0.033^\circ \text{C}^{-1}$$

Subtopic:  Derivation of Ohm's Law |
65%
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