Three voltmeters are connected as shown.

A potential difference has been applied between A and B. On closing the switch S, readings of volmeters?

(1) $V_1$ increases

(2) $V_1$ decreases

(3) $V_2<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>V_3$ both increase

(4) One of $V_2<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>V_3$ increases and other decreases

 

In the circuit in Fig. 7.27, bulb B does not glow although ammeter A indicates that the current is flowing. Why does the bulb not glow?

(1) The bulb is fused.

(2) There is a break in the circuit between bulb and ammeter.

(3) The variable resistor has too large resistance.

(4) There is a break in the circuit between the bulb and the variable resistance.

All bulbs in Fig. 7.30 are identical. Which bulb lights more brightly?

(1) 1

(2) 2

(3) 3

(4) 4

Which of the two switches $S_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>S_2$ shown in Fig. 7.31 will produce short circuiting?

(1) $S_1$

(2) $S_2$

(3) Both $S_1$ and $S_2$

(4) Neither $S_1$ nor $S_2$

Three similar light bulbs are connected to a constant voltage dc supply as shown in Fig. 7.32. Each bulb operates at normal brightness and the ammeter (of negligible resistance) registers a steady current. The filament of one of the bulbs breaks. What happens to the ammeter reading and to the brightness of the remaining bulbs?

  Ammeter reading                      Bulb brightness

a. increases                                     increases

b. increases                                     unchanged

c. unchanged                                   unchanged

d. decreases                                    unchanged

The circuit shown in Fig. 7.33 contains a battery, a rheostat, and two identical lamps. What will happen to the brightness of the lamps if the resistance of the rheostat is increased?

    Lamp P                Lamp Q

a. Less bright           Brighter

b. Less brighter        Less brighter

c. Brighter                Less brighter

d. No change             Brighter

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 $\Omega$