Electric power Formula

Electric power:

Let us illustrate some examples on power in electric circuit.

Electric power is defined as the rate of dissipation of electric energy or rate of doing work by the charges in an electric field.

Ex.1) Electric fan of power 1500 watt connected to 220 volt supply, find current drawn by electric fan.

Solution: Data,

P= 1500 watt,

V= 220 volt

Formula: P = V.I

On substituting the values in formula we get,

∴1500 =220×I

∴I = 1500/220

∴I = 6.82 A

Hence the current drawn by fan is 6.82 A.

Ex.2) Household water pump of 2 hp, uses 220 volt supply works for 1 hour daily, find current drawn and cost of electric energy spent by water pump in 10 days if electricity board charges Rs. 10 per unit

Solution: Data,

P= 2 hp= 2×746 = 1492 watt

P  = 1.492 kilowatt

V= 220 volt

Total time, t= 1 hr ×10= 10 hr

Formula: 1) = V.I , 2) E=P.t

On substituting the values in formula we get,

∴1492 = 220 × I

∴I = 1492/220

∴I = 6.78 A

Hence the current drawn by fan is 6.78 A.

Now using 2nd formula we can find total energy spent by water pump in 10 hr

∴E = 1.492×10

∴E = 14.92 unit.

Hence the total cost of energy = 14.92×10=149.2/- Rs

Ex.3) What is the power of bulb? If bulb is connected to a 240V generator and the current is 0.8 A.

Solution:

Given:

V = 240 V

I = 0.8 A

P = V × I

= 240 × 0.8

= 240 × 8/10

P = 192 W

The power of bulb is 192 W

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