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Standard IX

Physics

Power

If a bulb of ...

Question

If a bulb of 50 watts is used for 8 hours a day . How many unit it uses. How to find it?
what is the formula for it?

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Solution

By definition 1 watt= 1 joule/sec.

Hence, 50 watts= 50 joules/sec.

For 8 hr
Energy used= 50 x 3600 x 8 =1440000 J.

1 standard unit of electricity i.e. 1 kwh= 3600000 Joules.

So, units used by the 50 watts bulb for 8 hours = 1440000 / 3600000 = 0.4 units

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An electric bulb of rating $50 W$ is used for $8 hours$ a day. The number of units of energy used by the electric bulb in a day is:

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If a bulb of 50 watts is used for 8 hours a day . How many unit it uses. How to find it? what is the formula for it?

By definition 1 watt= 1 joule/sec. Hence, 50 watts= 50 joules/sec. For 8 hr Energy used= 50 x 3600 x 8 =1440000 J. 1 standard unit of electricity i.e. 1 kwh= 3600000 Joules. So, units used by the 50 watts bulb for 8 hours = 1440000 / 3600000 = 0.4 units

If a bulb of 50 watts is used for 8 hours a day . How many unit it uses. How to find it?
what is the formula for it?

By definition 1 watt= 1 joule/sec.

Hence, 50 watts= 50 joules/sec.

For 8 hr
Energy used= 50 x 3600 x 8 =1440000 J.

1 standard unit of electricity i.e. 1 kwh= 3600000 Joules.

So, units used by the 50 watts bulb for 8 hours = 1440000 / 3600000 = 0.4 units