Question 1 A body does 20 joules of work in 5 sec.what is its power?

Question 2 What is the power of a pump which takes 10 sec to lift 100 kg of water tank situated at a height of 20 m?

Question 3 Define the term power?

Question 4 Give the S.I. unit of power?

Question 5 Define the term watt?

Question 6 How many watts equal one horse power?

Question 7  The power output of an engine is 3 KW.How much work does the engine do in 20s?

Old man takes 10 min to do particular work whereas young man takes 5 min to do same work.
Power is defined as rate of doing work.

            work done
             Time taken
Power is work done per unit time.
When work is done,an equal amount of energy is consumed.
The S.I. unit of power is Watt(W)
1 watt is the power of an appliance which does work at rate of 1 joules per second.
                1 joule
1 Watt=————–
              1 Second

1 kilowatt=1000 watt
1KW = 1000 Watt
1 Megawatt=1000000 Watt
Another unit of power is horsepower(h.p.)
1 h.p. =746 watt
1 h.p. = 0.746 KW.
The commercial unit of energy is kilowatt-hour(KWh)
One KWh is the amount of electrical energy consumed when an electrical appliance having a power rating of 1Kw is used for 1 hr.
1 kilowatt-hour =1000 watts for 1 hour.
               1 joule
1 Watt=————–
                1 second

1kilowatt-hour = 36,00,000 joule

Watt or Kilowatt hour is unit of electrical power.
Kilowatt-hour is unit of electrical energy.
The electrical energy used in homes,shopes,industries is measured in kilowatt-hour(KWh)
1KWh of electrical energy is called as 1 unit of electricity.

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