Two cells of e.m.f. E₁ and E₂ are joined in series and the balancing length of the potentiometer wire is 625 cm. If the terminals of E₁ are reversed, the balancing length obtained is 125 cm. Given E₂>E₁, the ratio E₁:E₂ will be:

1. 2 : 3

2. 5 : 1

3. 3 : 2

4. 1 : 5

A 10 m long potentiometer wire is connected to a battery having a steady voltage. A Leclanche cell is balanced at 4 m length of the wire. If the length is kept the same, but its cross-section is doubled, the null point will be obtained at:

1. 8 m

2. 4 m

3. 2 m

4. None of these

Of the two bulbs in a household circuit, one glows brighter than the other. Which of the two bulbs has a large resistance?

1. The bright bulb

2. The dim bulb

3. Both have the same resistance

4. The brightness does not depend upon the resistance

Two electric bulbs whose resistances are in the ratio of 1 : 2, are connected in parallel to a constant voltage source. The power dissipated in them has the ratio of:

1. 2 : 1

2. 1 : 1

3. 1 : 4

4. 1 : 2

Three identical bulbs B₁, B₂ and B₃ are connected to the mains as shown in the figure. If B₃ is disconnected from the circuit by opening switch S, then incandescence of bulb B₁ will:

1. Increase

2. Decrease

3. Become zero

4. No change

A 50 W bulb connected in series with a heater coil is put to an AC mains. Now the bulb is replaced by a 100 W bulb. The heater output will

1. Double

2. Halve

3. Increase

4. Decrease

Two heater coils separately take 10 minutes and 5 minutes to boil a certain amount of water. If both the coils are connected in series, the time taken will be:

1. 15 min

2. 7.5 min

3. 3.33 min

4. 2.5 min

The power generated across a uniform wire connected across a supply is H. If the wire is cut into n equal parts and all the parts are connected in parallel across the same supply, the total power generated in the wire is:

1. $\frac{H}{n^2}$

2. n²H

3. nH

4. $\frac{H}{n}$

When electric bulbs of the same power, but different marked voltage are connected in series across the power line, their brightness will be:

1. proportional to their marked voltage.

2. inversely proportional to their marked voltage.

3. proportional to the square of their marked voltage.

4. the same for all of them.

A battery consists of a variable number n of identical cells having internal resistance connected in series. The terminals of the battery are short-circuited and the current I measured. Which one of the graph below shows the relationship between I and n?

1. 

2. 

3. 

4.