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 is drawn 500 W is

Question

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 is drawn 500 W is (A) 18 Ω (B) 20 Ω (C) 40 Ω (D) 700 Ω

Tardigrade Admin · Accepted Answer

P=VI, I=(P/V) or I=(500 W/100 V)=5 A Now, 5R=100 or R=20 Ω .

Q. 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 is drawn $500 W$ is

$18$ $Ω$

$20$ $Ω$

$40$ $Ω$

$700$ $Ω$

$P = V I, I = \frac{P}{V}$
or $I = \frac{500 W}{100 V} = 5 A$
Now, $5 R = 100$
or $R = 20 Ω$ .

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

18 Ω

20 Ω

40 Ω

700 Ω