# When no current is passed through a conductor, (a) the free electrons do not move. (b) the average speed of a free electron over a large period of time is zero. (c) the average velocity of a free electron over a large period of time is zero. (d) the average of the velocities of all the free electrons at an instant is zero. Choose the correct option:  1. (a) only  2. (b), (c) 3. (c), (d)  4. (a), (d)

Subtopic:  Current & Current Density |
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As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity:

 1 increases 2 decreases 3 remains constant 4 may increase or decrease
Subtopic:  Derivation of Ohm's Law |
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A uniformly increasing current flows through a $$30$$ $$\Omega$$ resistance, as shown in the graph.

The thermal energy generated in the resistance due to Joule heating is:
1. $$240$$ J
2. $$480$$ J
3. $$160$$ J
4. $$320$$ J
Subtopic:  Heating Effects of Current |
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In a Wheatstone Bridge arrangement, as shown in the figure, the bridge is balanced. However, when the resistances in the arms P, Q are switched, the bridge is balanced only when $$R$$ is replaced by $$4R$$ in the other two arms. If the value of R is $$100$$ $$\Omega$$, that of S is:

1. $$100$$ $$\Omega$$
2. $$50$$ $$\Omega$$
3. $$200$$ $$\Omega$$
4. $$400$$ $$\Omega$$
Subtopic:  Wheatstone Bridge |
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A wire is connected to form an equilateral triangle ABC, each side having a resistance of $$4$$ $$\Omega$$. The vertex C is maintained at zero volts ($$V_C=0$$), and currents flowing in at A and B are as shown in the figure. The ratio of the potentials at D and E $$\Big(i.e.~\frac{V_D}{V_E}\Big)$$ equals:

1. $$\frac31$$

2. $$\frac21$$

3. $$\frac11$$

4. $$\frac53$$
Subtopic:  Kirchoff's Current Law |
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AB is a $$20$$ $$\Omega$$ resistor with a tapping point C that can be moved along AB. The resistances in AC, BC are proportional to the lengths AC, BC. Initially, C is at the mid-point of AB and the circuit is switched on.

If the tapping point C is moved so that the length BC is reduced to half its initial value, then the voltage across the $$15$$ $$\Omega$$ resistor,

 1 increases by $$1$$ V 2 decreases by $$1$$ V 3 increases by $$3$$ V 4 decreases by $$3$$ V

Subtopic:  Kirchoff's Voltage Law |
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Given below are two statements:
 Statement I: The law of conservation of energy is valid in electric circuits. Statement II: Kirchhoff's junction law is applicable to electric circuits.

 1 Statement I and Statement II are True and Statement I is the correct explanation of Statement II. 2 Statement I and Statement II are True and Statement I is not the correct explanation of Statement II. 3 Statement I is True, Statement II is False. 4 Statement I is False, Statement II is True.
Subtopic:  Kirchoff's Current Law |
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All the cells, shown in the figure below, are of $$2$$ V, and all the resistances are $$1$$ $$\Omega$$. When a potential difference $$V$$ is applied between A and B, the current through the circuit doubles compared to the situation when the potential difference is made zero.
Then,

 1 $$V=2$$ volt, positive at A. 2 $$V=2$$ volt, negative at A. 3 $$V=6$$ volt, positive at A. 4 $$V=6$$ volt, negative at A.

Subtopic:  Kirchoff's Voltage Law |
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All the resistances in the circuit shown below are $$2~\Omega.$$ The equivalent resistance between $$A$$ and $$C$$ is:

1. $$4~\Omega$$
2. $$2~\Omega$$
3. $$\frac43~\Omega$$
4. $$\frac{10}3~\Omega$$
Subtopic:  Combination of Resistors |
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The current flowing through the left $$20~\Omega$$ resistor is:
 1 $$1$$ A 2 $$0.5$$ A 3 $$2.5$$ A 4 $$3$$ A