Current Electricity

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

1. 26%
2. 36%
3. 46%
4. 56%

The resistance per centimeter of a meter bridge wire is r, with X resistance in left gap. Balancing length from left end is at 40 cm with 25 resistance in right gap. Now the wire is replaced by another wire of 2r resistance per centimeter. The new balancing length for same settings will be at

1. 10 cm
2. 80 cm
3. 40 cm
4. 20 cm

In the following circuit, the battery has an emf of 2 V and an internal resistance of 23 . The power consumption in the entire circuit is W. [figure]

A potential divider circuit is shown in figure. The output voltage V0 is : [figure]

1. 2 mV
2. 4 V
3. 0.5 V
4. 12 mV

An electric toaster has resistance of 60 at room temperature (27 ). The toaster is connected to a 220 V supply. If the current flowing through it reaches 2.75 A, the temperature attained by toaster is around : ( if =2 10-4/ )

1. 1235
2. 1667
3. 694
4. 1694

Two cells are connected in opposition as shown. Cell E1 is of 8 V emf and 2 internal resistance; the cell E2 is of 2 V emf and 4 internal resistance. The terminal potential difference of cell E2 is V. [figure]

When a potential difference V is applied across a wire of resistance R, it dissipates energy at a rate W. If the wire is cut into two halves and these halves are connected mutually parallel across the same supply, the energy dissipation rate will become:

1. 1/2W
2. 4W
3. 1/4W
4. 2W

Two resistances of 100 and 200 are connected in series with a battery of 4 V and negligible internal resistance. A voltmeter is used to measure voltage across 100 resistance, which gives reading as 1 V. The resistance of voltmeter must be .

The electric current through a wire varies with time as I=I0+ t, where I0=20 A and =3 A/s. The amount of electric charge crossed through a section of the wire in 20 s is :

1. 80 C
2. 800 C
3. 1000 C
4. 1600 C

In the given circuit, the current in resistance R3 is : [figure]

1. 2 A
2. 1.5 A
3. 1 A
4. 2.5 A