Question

A bulb is rated as 250 V; 0.4 A. Find its (i) power, and (ii) resistance.; A bulb is rated as 250 V; 0.4 A. Find its (i) power, and (ii) resistance.

Answer 1

(i) Bulb power is 100 watts.

(ii) Bulb resistance is 625 Ohms.

Explanation:

Given : A bulb is rated as 250 V; 0.4 A.

(i) Power of bulb is given by

$p = v \times i$

$p = 250 \times 0.4$

$p = 100 \: watts$

The power of bulb is 100 watts.

(ii) The resistance of bulb is given by

$r = \frac{v}{i}$

$r = \frac{250}{0.4}$

$r = 625 \: ohms$

The bulb resistance is 625 ohms.

Answer 2

Power = 100 watt

Resistance = 0.0016 ohm

explanation:

Given,

v = 250 volt

current ,i = 0.4 amp

i. Power = ?

We know that,

P = VI

P = 250\times 0.4

p = 100 watt

ii. resistance  = ?

We know that,

power, P = VI      ∵ V = IR

P = $I^2 \times R$

∴ R = $\frac {P}{I^2}$

  R = $\frac{100}{0.4 \times 0.4}$

  R = 625 ohm