Question

an electric bulb is rated 220 V and 100 Watts. when it is operated on 110 V, the power consumed will be? Calculate using only this formula P=VI​

Answer 1

Answer:

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Explanation:

R = 220^2/100 Ω = 484 Ω. This is the resistance of the bulb. When V= 110 V, power consumed = V^2/R = 110^2/484 = 25 W. So, 25 W power is consumed when it isoperated on 110 V.

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Answer 2

$\bf{\underline{In\:the\:first\:case:-}}$

Given :-

• Power (p) = 100 w

• potential difference (v) = 220 v

To find :-

• Resistance (R) = ?

Solution :-

we know that,

✭ ${\underline{\boxed{\bf\red{p=\dfrac{{v}^{2}}{R}}}}}$

$\rm\longrightarrow\:100=\dfrac{(220)^2}{R}$

$\rm\longrightarrow\:R=\dfrac{220\times\:220}{100}$

$\rm\longrightarrow\:R=484\:\Omega\:$

Hence, the resistance will be 484 Ω .

$\bf{\underline{In\:the\:second\:case:-}}$

Given :-

• Potential difference (v) = 110 v

• Resistance (R) = 484 Ω (calculated in the first case)

To find :-

• Power (p) = ?

Solution :-

we know that,

✭ ${\underline{\boxed{\bf\pink{p=\dfrac{{v}^{2}}{R}}}}}$

$\rm\longrightarrow\:p=\dfrac{(110)^2}{484}$

$\rm\longrightarrow\:p=\dfrac{110\times\:110}{484}$

$\rm\longrightarrow\:p=25\:W$

Hence,the power consumed will be 25 W.