Current Electricity

The resistance of each arm of the Wheatstone's bridge is 10 ohm. A resistance of 10 ohm is connected in series with a galvanometer then the equivalent resistance across the battery will be

1. 10 ohm
2. 15 ohm
3. 20 ohm
4. 40 ohm

If specific resistance of a potentiometer wire is 10-7 m and current flow through it is 0.1 amp., cross-sectional area of wire is 10-6 m2 then potential gradient will be

1. 10-2 volt/m
2. 10-4 volt/m
3. 10-6 volt/m
4. 10-8 volt/m

The net resistance of the circuit between A and B is [figure]

1. 83
2. 143
3. 163
4. 223

A car battery of emf 12 V and internal resistance 5 10-2 , receives a current of 60 amp, from external source, then terminal potential difference of battery is

1. 12 V
2. 9 V
3. 15 V
4. 20 V

Two bulbs of (40 W, 200 V), and (100 W, 200 V). Then correct relation for their resistances

1. R40 < R100
2. R40 > R100
3. R40 = R100
4. no relation can be predicted.

The potentiometer is best for measuring voltage, as

1. it has a sensitive galvanometer and gives null deflection
2. it has wire of high resistance
3. it measures p.d. in closed circuit
4. it measures p.d. in open circuit.