Current Electricity

Ten identical cells connected in series are needed to heat a wire of length one meter and radius 'r' by 10 in time 't'. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time 't' ?

1. 20
2. 30
3. 40
4. 10

A cell having an emf and internal resistance r is connected across a variable external resistance R. As the resistance R is increased, the plot of potential difference V across R is given by

1. [figure]
2. [figure]
3. [figure]
4. [figure]

The power dissipated in the circuit shown in the figure is 30 watts. The value of R is [figure]

1. 20
2. 15
3. 10
4. 30

In the circuit shown the cells A and B have negligible resistances. For VA = 12 V, R1 = 500 and R = 100 the galvanometer (G) shows no deflection. The value of VB is [figure]

1. 4 V
2. 2 V
3. 12 V
4. 6 V

A ring is made of a wire having a resistance R0 = 12 . Find the points A and B, as shown in the figure, at which a current carrying conductor should be connected so that the resistance R of the sub circuit between these points is equal to 83 . [figure]

1. l1l2 = 58
2. l1l2 = 13
3. l1l2 = 38
4. l1l2 = 12

If voltage across a bulb rated 220 volt-100 watt 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%

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

1. +1 V
2. -1 V
3. +2 V
4. -2 V

A current of 2 A flows through a 2 Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 Ω resistor. The internal resistance of the battery is

1. 0.5 Ω
2. 1/3 Ω
3. 1/4 Ω
4. 1 Ω

If power dissipated in the 9 Ω resistor in the circuit shown is 36 watt, the potential difference across the 2 Ω resistor is [figure]

1. 4 volt
2. 8 volt
3. 10 volt
4. 2 volt

Consider the following two statements. Which of the following is correct?

1. Both (A) and (B) are wrong
2. (A) is correct and (B) is wrong
3. (A) is wrong and (B) is correct
4. Both (A) and (B) are correct