Question

Two electric lamps of 40W, 200v rating are connected in parallel across the mains (220V). The net power consumed by them is?

Answer 1

HEY!!

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⏺️Va=200 V

⏺️Vs=220 V

⏺️Power of lamp, P=40 W

⏺️R=V^/2P

⏺️Also, lamp are connected in parallel. 

⏺️Req= R/2

⏺️Req=Va^2/2P

⏺️Req=(200)^2/2×40= 500 ohm

⏺️Net Power, P'=Vs^2/Req

⏺️⏺️P'=(220)^2/500= 96.8 W

Answer 2

The net power consumed by them is 96.8 W.

Explanation:

Given that,

Power of lamp= 40 W

Applies voltage = 200 V

Supplies voltage = 220 V

We know that,

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

Lamp are connected in parallel

We need to calculate the equivalent resistance

Using formula of resistance

$Req=\dfrac{R}{2}$

Put the value of R into the formula

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

$Req=\dfrac{200^2}{2\times40}$

$Req=500\ \Omega$

We need to calculate the net power consumed

Using formula of power

$P=\dfrac{V_{s}^2}{Req}$

$P=\dfrac{220^2}{500}$

$P=96.8\ W$

Hence, The net power consumed by them is 96.8 W.

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Topic : Power consumed

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