Electric Power
Electric Power
Power is the rate of doing work, or the rate at which energy is produced or consumed. It is defined as the amount of electric energy consumed in a circuit per unit time.
If W be the amount of electric energy consumed in a circuit in t seconds, then the electric power is given by
But electrical energy can be defined as
According to Ohm s law,
Substituting the value in the equation we get
Units of Power:
The SI unit of electric power is watt (W).
Electric power is said to be1 watt, if 1 ampere current flows through a circuit having 1 volt potential difference.
i.e.,
Bigger units of power are as given below:
1 kilowatt (kW) =
1 megawatt (MW) =
1 gigawatt (GW) =
2. Practical unit of power is horse power.
1 HP = 746 W
3. Commercial unit of electrical energy
4. Number of units consumed by electric appliances is
Are electrons consumed in an electric circuit ?
No electrons are not consumed in an electric circuit. We pay the electricity board or electric company to provide energy to move electrons through all the electric gadgets like fan, bulb, refrigerator, etc. installed in our homes. We pay for the electricity that we use.
Illustration: An electric refrigerator rated 500W operates 6 hours/day. What is the costof the energy to operate it for 30 days at Rs. 4.5 per kWh?
Solution: Energy consumed by refrigerator in 30 days
Cost of energy to operate the refrigerator for 30 days
An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it ? | |||
| Right Option : D | |||
| View Explanation | |||
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be ____________ | |||
| Right Option : D | |||
| View Explanation | |||
An electric bulb is rated 220 V and 40W.When it is operated on 110V,the power consumed will be- | |||
| Right Option : A | |||
| View Explanation | |||
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