A battery is charged at a potential of 15V for 8h when the current flowing is 10A. The battery on discharge supplies a current of 5A for 15h. The mean terminal voltage during discharge is 14V. 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. A battery of V volts is connected between A and B. The current flowing in AFCEB will be

1. $\frac{V}{R}$

2. $\frac{V}{2R}$

3. $\frac{2V}{R}$

4. $\frac{3V}{R}$

Two batteries, one of emf 18 V and internal resistance $2\mathrm{\Omega }$ and the other of emf 12 V and internal resistance $1\mathrm{\Omega }$, are connected as shown. The voltmeter V will record a reading of

1. 18 V

2. 30 V

3. 14 V

4. 15 V

For the network shown in the figure, the value of the current i is

1. $\frac{18V}{5}$

2. $\frac{5V}{9}$

3. $\frac{9V}{35}$

4. $\frac{5V}{18}$

Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances ${\mathrm{r}}_1$ and ${\mathrm{r}}_2({\mathrm{r}}_1>{\mathrm{r}}_2)$ respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is

1. ${\mathrm{r}}_1-{\mathrm{r}}_2$

2. $\frac{r_1+r_2}{2}$

3. $\frac{r_1-r_2}{2}$

4. $r_1+r_2$

The total power dissipated in Watts in the circuit shown here is

1. 4

2. 16

3. 30

4. 54

An electric kettle takes 4A current at 220 V. How much time will it take to boil 1kg of water from temperature $20°\mathrm{C}$? The temperature of boiling water is $100°\mathrm{C}$ .

1. 4.2 min

2. 6.3 min

3. 8.3 min

4. 12.6 min

A cell can be balanced against 110 cm and 100 cm of the potentiometer wire, respectively with and without being short circuited through a resistance of $10\mathrm{\Omega }$. Its internal resistance is

1. zero

2. $1.0\mathrm{\Omega }$

3. $0.5\mathrm{\Omega }$

4. $2.0\mathrm{\Omega }$

A wire of resistance 12  $\mathrm{\Omega }$ is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points, A and B as shown in the figure is

1. $3\mathrm{\Omega }$

2. $6\mathrm{\pi \Omega }$

3. $6\mathrm{\Omega }$

4. $0.6\mathrm{\pi \Omega }$

See the electrical circuit shown in the figure below. Which of the following equations is a correct equation for it?

1.${\mathrm{\epsilon }}_2-{\mathrm{i}}_2{\mathrm{r}}_2-{\mathrm{\epsilon }}_1+{\mathrm{i}}_1{\mathrm{r}}_1=0$

2. $-{\mathrm{\epsilon }}_2-({\mathrm{i}}_1+{\mathrm{i}}_2)\mathrm{R}+{\mathrm{i}}_2{\mathrm{r}}_2=0$

3. ${\mathrm{\epsilon }}_1-({\mathrm{i}}_1+{\mathrm{i}}_2)\mathrm{R}+{\mathrm{i}}_1{\mathrm{r}}_1=0$

4. ${\mathrm{\epsilon }}_1+({\mathrm{i}}_1+{\mathrm{i}}_2)\mathrm{R}-{\mathrm{i}}_1{\mathrm{r}}_1=0$