A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn becomes 10I. The value of 'n' is:-

1. 10

2. 11

3. 20

4. 9

Which of the following acts as a circuit protection device?

1. fuse

2. conductor

3. inductor

4. switch

Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 The power loss in the wire is:

1. 19.2 W

2. 19.2 kW

3. 19.2 J

4. 12.2 kW

If voltage across a bulb rated 220 V-100 W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is :

1. 20%

2. 2.5%

3. 5%

4. 10%

The resistance of an ammeter is 13 Ω and its scale is graduated for a current up-to 100 A. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up-to 750 A by this meter. The value of shunt resistance is:

1. 20$\Omega$

2. 2 $\Omega$

3. 0.2$\Omega$

4. 2 k$\Omega$

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately :

1. 30%

2. 50%

3. 90%

4. 10%

A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves:-

1. Potential gradients

2. A condition of no current flow through the galvanometer

3. A condition of cells, galvanometer, and resistances

4. Cells