Current Electricity

Two resistors of 200 Ω and 400 Ω are connected in series with a battery of 100 V. A bulb rated at 200 V, 100 W is connected across the 400 Ω resistance. The potential drop across the bulb is V.

1. 25
2. 50
3. 66.6
4. 100

For the two cells having same EMF E and internal resistance r, the current passing through the external resistor 6 is same when both the cells are connected either in parallel or in series. The value of internal resistance r is .

1. 3
2. 6
3. 4
4. 9

In the potentiometer, when the cell in the secondary circuit is shunted with 4 resistance, the balance is obtained at the length 120 cm of wire. Now when the same cell is shunted with 12 resistance, the balance is shifted to a length of 180 cm. The internal resistance of cell is

1. 4
2. 12
3. 6
4. 3

The equivalent resistance between the points A and B in the following circuit is x5 . The value of x is . [figure]

A Wheatstone bridge is initially at room temperature and all arms of the bridge have same value of resistances (R1 = R2 = R3 = R4). When R3 resistance is heated to some temperature, its resistance value has gone up by 10%. The potential difference (Va - Vb) (after R3 is heated) is V. [figure]

1. 1.05
2. 0.95
3. 0
4. 2

Two resistors of 100 each are connected in series with a 9 V battery. A voltmeter of 400 resistance is connected to measure the voltage drop across one of the resistors. The voltmeter reading is V.

1. 3
2. 2
3. 4
4. 4.5

Two resistors 2 and 3 are connected in the gaps of bridge as shown in figure. The null point is obtained with the contact of jockey at some point on wire XY. When an unknown resistor is connected in parallel with 3 resistor, the null point is shifted by 22.5 cm toward Y. The resistance of unknown resistor is . [figure]

1. 3
2. 1
3. 4
4. 2

The reading of the ammeter (A) in steady state in the following circuit (assuming negligible internal resistance of the ammeter) is A. [figure]

1. 1/2
2. 1
3. 2
4. 0

A regular hexagon is formed by six wires each of resistance r and the corners are joined to the centre by wires of same resistance. If the current enters at one corner and leaves at the opposite corner, the equivalent resistance of the hexagon between the two opposite corners will be

1. 35r
2. 45r
3. 58r
4. 34r

In a meter bridge experiment to determine the value of unknown resistance, first the resistances 2 and 3 are connected in the left and right gaps of the bridge and the null point is obtained at a distance l cm from the left. Now when an unknown resistance x is connected in parallel to 3 resistance, the null point is shifted by 10 cm to the right of wire. The value of unknown resistance x is .