The SI unit of power is watt.
The power of an agent is one watt if it does work at the rate of 1 joule per second or if it consumes energy at the rate of 1 joule per second.
It can be expressed as:
1 megawatt = 1000,000 watts or 1 MW =1000,000 W or
Power of motor vehicles and other machines are given in terms of Horsepower (hp).
1 Horse power = 746 watts or 1 H.P. = 746 W
The power at any given instant of time is called instantaneous power.
Average-power is defined as the total energy consumed divided by the total time taken.
Power is always dependent on work done.
If a person does work at different rates his power also differs at different times. In such cases the concept of average-power is used.
Consider Bulb A of 60 watt bulb is switched ON 24 hours a day and there is another Bulb B of 60 watt turned ON for only 12 hours. Given the context, calculate the energy consumed by both the bulbs in one day.
For the first 12 hours both bulb A and B are turned ON therefore,
Now for the next 12 hours only bulb A would remain ON:
power = 60 watt
energy = power x time
= 120 x 12 = 1.44 kWh (kilo watt hour)
The power consumed during the whole day varies because one bulb is turned ON for only 12 hours so we need to calculate average power,
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