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% 

Five equal resistances each of resistance R are connected as shown in the figure below. A battery of V volts is connected between A and B. The current flowing in AFCEB will be:

1. V/R

2. V/2R

3. 2V/R

4. 3V/R

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

1. 3 V

2. 1 V

3. 1.5 V

4. 2 V

The specific resistance of a conductor increases with:

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

1. \(\frac{10}{9}~ \Omega\)
2. \(\frac{9}{10}~ \Omega\)
3. \(\frac{11}{9}~ \Omega\)
4. \(\frac{5}{9}~ \Omega\)

If the specific resistance of a potentiometer wire is ${10}^{-7}$ $\Omega m$ and the current flow through it is 0.1 A, the cross-sectional area of the wire is  ${10}^{-6}$ $m^2$, then potential gradient will be:

1. ${10}^{-2}$ $V/m$

2. ${10}^{-4}$ $V/m$

3. ${10}^{-6}$ $V/m$

4. ${10}^{-8}$ $V/m$

The resistance of each arm of the wheat stone bridge is \(10~ \Omega.\) A resistance of \(10~ \Omega\) is connected in series with a galvanometer. The equivalent resistance across the battery will be:
1.\(10~ \Omega\)
2.\(15~ \Omega\)
3. \(20~ \Omega\)
4. \(40~ \Omega\)

If copper and silicon are cooled from 300 K to 60 K, then the specific resistance will:
1.  Decrease in copper but increase in silicon
2.  Increase in copper but decrease in silicon
3.  Increase in both
4.  Decrease in both

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 min
2. 4 min
3. 25 min
4. 15 min