The potentiometer is best for measuring voltage, as:

1. It has a sensitive galvanometer
2. It has wire of high resistance
3. It measures p.d. like in closed circuit
4. It measures p.d. like in open circuit

When three identical bulbs of 60 watts and 200-volt rating are connected in series to a 200-volt supply, the power drawn by them will be:

1. 180 watts
2. 10 watts
3. 20 watts
4. 60 watts

The electric resistance of a particular wire of iron is R. If its length and radius are doubled, then:
 

Resistances n, each of r ohm, when connected in parallel give an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have resistance in ohms, equal to:

1. $\frac{\mathrm{R}}{{\mathrm{n}}^2}$

2. R/n

3. nR

4. n² R 

The current in 8 Ω resistance is (in the figure below):

1.  0.69 A
2.  0.92 A
3.  1.30 A
4.  1.6 A

If the power dissipated in 5 Ω is 20 W then the power dissipated in 4 Ω is:
   

1.  4 W

2. 6 W

3. 10 W 

4. 20 W

The value of R for which power in it is maximum is:

1. 3 Ω
2. 6 Ω
3. 12 Ω
4. 9 Ω

The terminal potential difference of a cell is greater than its emf when:

In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in the USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in the USA will be:

1. 2R
2. R/4
3. R/2
4. R 

A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharges is 14 V. The "Watt hour" efficiency of the battery is:

1. 80%

2. 90%

3. 87.5%

4. 82.5%