Current Electricity

A 6 volt battery is connected to the terminals of a three metre long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be

1. 2 volt
2. 3 volt
3. 1 volt
4. 1.5 volt

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

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

In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in 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 USA will be

1. R
2. 2R
3. R/4
4. R/2

In a Wheatstone's bridge all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is

1. R/4
2. R/2
3. R
4. 2R

Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be

1. 50 watt, 100 watt
2. 100 watt, 50 watt
3. 200 watt, 150 watt
4. 50 watt, 200 watt

An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be

1. 8 minutes
2. 4 minutes
3. 25 minutes
4. 15 minutes

Fuse wire is a wire of

1. high resistance and high melting point
2. high resistance and low melting point
3. low resistance and low melting point
4. low resistance and high melting point

For a cell terminal potential difference is 2.2 V when circuit is open and reduces to 1.8 V when cell is connected to a resistance of R = 5 . Determine internal resistance of cell (r)

1. 109
2. 910
3. 119
4. 59

Specific resistance of a conductor increases with

1. increase in temperature
2. increase in cross-section area
3. increase in cross-section and decrease in length
4. decrease in cross-section area.

Copper and silicon are cooled from 300 K to 60 K, the specific resistance

1. decrease in copper but increase in silicon
2. increase in copper but decrease in silicon
3. increase in both
4. decrease in both