A potentiometer circuit has been setup for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of

(i)infinity

(ii)9.5Ω 

the 'balancing lengths', on the potentiometer wire are found to be 3m and 2.85m, respectively. The value of internal resistance of the cell is

(1) 0.25Ω 

(2) 0.95Ω 

(3) 0.5Ω 

(4) 0.75Ω  

In the circuit shown the cells A and B have negligible resistances. For $V_A=12V, R_1=500\Omega and R=100\Omega$ the galvanometer (g) shown no deflection.The value of $V_B$ is 

(a)4V                                         (b)2V

(c)12V                                       (d)6V

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 power dissipated in the circuit shown in

the figure is 30 Watt. The value of R is :

(1) $20\mathrm{\Omega }$

(2) $15\mathrm{\Omega }$

(3) $10\mathrm{\Omega }$

(4) $30\mathrm{\Omega }$

If power dissipated in the 9$\mathrm{\Omega }$ resistor in the circuit 

shown is 36 W, the potential difference across 

the 2$\mathrm{\Omega }$ resistor is

(a) 8 V

(b) 10 V

(c) 2 V

(d) 4 V

In the circuit in the figure, if the potential at point A is taken to be zero, the potential at point B is :

1. -1V                                          2. +2V

3. -2V                                          4. +1V

A wire of resistance $12 {\mathrm{\Omega m}}^{-1}$ 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 :

(a) $0.6 \mathrm{\pi } \mathrm{\Omega }$                                               (b) $3 \mathrm{\Omega }$

(c) $6 \mathrm{\pi } \mathrm{\Omega }$                                                  (d) $6 \mathrm{\Omega }$

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

1. ${\epsilon }_1-\left(i_1+i_2\right)R-i_1{r}_1=0$

2. ${\epsilon }_2-i_2{r}_2-{\epsilon }_1-i_1{r}_1=0$

3. $-{\epsilon }_2-\left(i_1+i_2\right)R+i_2{r}_2=0$

4. ${\epsilon }_1-\left(i_1+i_2\right)R+i_1{r}_1=0$

A wire of a certain material is streched slowly by ten per cent. Its new resistance and specific resistance become respectively 

(1) 1.2 times, 1.1 times

(2) 1.21 times,same 

(3) both remain the same

(4) 1.1 times, 1.1 times

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

(a) 6.3 min

(b) 8.4 min

(c) 12.6 min

(d) 4.2 min