Question

An electric bulb marked 40W-200V is used in a circuit of supply voltage 100V. Now its power is:

Answer 1

Power of the bulb is 10 Watts.

Step-by-step explanation:

We have,

Power and voltage of electric bulb is 40 W and 200 V. Using this data we can find the resistance of the bulb.

Power,
`P=(V^2)/(R)`

R is resistance

`R=(V^2)/(P)\\\\R=((200)^2)/(40)\\\\R=1000\ \Omega`

The supplied voltage is 100 V.

Now power is given by :

`P=(V^2)/(R)\\\\P=(100^2)/(1000)\\\\P=10\ W`

So, now the power of the bulb is 10 Watts.