Current Electricity

Two wires A and B are made up of the same material and have the same mass. Wire A has radius of 2.0 mm and wire B has radius of 4.0 mm. The resistance of wire B is 2 . The resistance of wire A is .

The reading in the ideal voltmeter (V) shown in the given circuit diagram is : [figure]

1. 3 V
2. 10 V
3. 5 V
4. 0 V

The current in a conductor is expressed as I = 3t2 + 4t3, where I is in Ampere and t is in second. The amount of electric charge that flows through a section of the conductor during t = 1 s to t = 2 s is C.

In a metre-bridge when a resistance in the left gap is 2 and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 , the balance length changes by :

1. 62.5 cm
2. 22.5 cm
3. 20 cm
4. 65 cm

To measure the temperature coefficient of resistivity of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor. The experiment is being conducted at 25 and resistance of the semiconductor arm is 3 m . Arm BC is cooled at a constant rate of 2 /s. If the galvanometer G shows no deflection after 10 s, then is : [figure]

1. -1 10-2 C-1
2. -2 10-2 C-1
3. -2.5 10-2 C-1
4. -1.5 10-2 C-1

In an electrical circuit drawn below the amount of charge stored in the capacitor is . [figure]

Two conductors have the same resistances at 0 C but their temperature coefficients of resistance are 1 and 2. The respective temperature coefficients for their series and parallel combinations are :

1. 1+ 2, 1 2 1+ 2
2. 1+ 22, 1+ 22
3. 1+ 2, 1+ 22
4. 1+ 22, 1+ 2

Equivalent resistance of the following network is . [figure]

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

1. 26%
2. 36%
3. 46%
4. 56%

The resistance per centimeter of a meter bridge wire is r, with X resistance in left gap. Balancing length from left end is at 40 cm with 25 resistance in right gap. Now the wire is replaced by another wire of 2r resistance per centimeter. The new balancing length for same settings will be at

1. 10 cm
2. 80 cm
3. 40 cm
4. 20 cm