Two similar headlight lamps are connected in parallel to each other. Together, they consume 48 W from a 6 V battery. What is the resistance of each filament?

(1) 6 $\Omega$

(2) 4 $\Omega$

(3) 3.0 $\Omega$

(4) 1.5 $\Omega$

Two electric bulbs, rated for the same voltage, have powers of 200 W and 100 W, respectively. If their resistances are $r_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>r_2$, respectively then :

1. $r_1=2r_2$

2. $r_2=2r_1$

3. $r_2=4r_1$

4. $r_1=4r_2$

If the current in an electric bulb decreases by 0.5%, the power in the bulb decreases by approximately :

(1) 1%

(2) 2%

(3) 0.5%

(4) 0.25%

An electric bulb rated for 500 W at 100 V is used in a circuit having a 200 V supply. The resistance R that must be put in series with the bulb, so that the bulb draws 500 W, is :

(1) 18 $\Omega$

(2) 20$\Omega$

(3) 40 $\Omega$

(4) 700 $\Omega$

A wire, when connected to a \(220~\text{V}\) mains supply, has power dissipation \(P_1.\) Now, the wire is cut into two equal pieces, which are connected in parallel to the same supply. Power dissipation in this case is \(P_2.\) Then \(P_2:P_1\)  is :
(1) 1

(2) 4

(3) 2

(4) 3

Three bulbs of 40 W, 60 W, and 100 W are connected in series with a 240 V source. Then,

(1) The potential difference will be the maximum across the 40 W bulb.

(2) The current will be the maximum in 100 W bulb.

(3) The resistance of the 40 W bulb is the minimum.

(4) The current through the 60 W bulb will be 0.1 A.

The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?

(1) 14,000 $\Omega$

(2) 400 $\Omega$

(3) 40 $\Omega$

(4) 4 $\Omega$

Two electric bulbs A and B are rated 60 W and 100 W, respectively. If they are connected in parallel to the same source, then,

(1) both the bulbs draw the same current

(2) bulb A draws more current than bulb B

(3) bulb B draws more current than bulb A

(4) currents drawn in the bulbs are in the ratio of their resistances

Figure 7.44 shows three similar lamps $L_1,<mspace\; width="1em"></mspace>L_2<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>L_3$ connected across a power supply. If the lamp $L_3$ fuses, how will the light emitted by $L_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>L_2$ change?

(1) no change

(2) brilliance of both $L_1$ decreases and that of $L_2$ increases

(3) brilliance of both $L_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>L_2$ increases

(4) brilliance of both $L_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>L_2$ decreases

A factory is served by a 220 V supply line. In a circuit protected  by a fuse marked 10 A, the maximum number of 100 W lamps in parallel that can be turned on is :

1. 11 

2. 22

3. 33

4. 66