Current Electricity — Question 5

nearly 25 W

Reason — Given,

Power (P) = 100 W

Voltage (V) = 220 V

We know that,

Power (P) = VI

Substituting the values in the formula above, we get,

100 = 220 x I

⇒ I = $\dfrac{100}{220}$

⇒ I = 0.45 A

Hence, current through the lamp = 0.45 A

Power consumed when voltage is 110 V = ?

Resistance of lamp (R) = $\dfrac{V^2}{P}$

Substituting the values in the formula, we get,

$R = \dfrac{220^2}{100} \\[0.5em] \Rightarrow R = 484 Ω$

From relation,

P = $\dfrac{V^2}{R}$

Substituting the values in the formula, we get,

$P = \dfrac{110^2}{484} \\[0.5em] \Rightarrow P = 25 W$

Hence, power consumed is 25 W