Power (P) Energy transferred or work done per unit of time is the measure of the rate at which work is done or energy is being transferred from one form to another.
The basic formula for power (P) is: P=Wt
Where:
P = Power
W = Work done (or energy transferred)
t = Time
SI Unit: The unit of power in the International System of Units (SI) is the watt (W).
1 watt = 1 joule/second (1 W = 1 J/s)
For any electrical circuit, the power is calculated using these three equations
In terms of Voltage and current, it is expressed as
P = V×I
In terms of current and resistance, it is expressed as
P=I2R
Voltage and resistance, It is expressed as
P=V2R
Where,
A voltage applied across the two ends =V,
Current flowing in the circuit = I and
Resistance = R
The formula of Power is utilized to calculate the Power, Resistance, Voltage, or current in an electric circuit. The standard unit of power, in metric, is the Watt.
Solved Examples
Problem 1: An electric machine uses 300 J energy to do work in 10s. What power does it employ?
Answer:
Given: Work done = W = 300 J,
Time taken t = 10 s.
The power used by it is given as
Problem 2: John, who has a mass of 60 kg runs up to 12m high in 40 seconds. Calculate his power.
Answer:
Known: m (mass) = 60 kg,
h = height = 12 m,
t (time taken) = 40 seconds.
Power is given by:
Understanding power allows one to analyze how efficiently work is done or how energy is used. Mastery of the basic formula and its applications is indispensable in solving problems both in physics and real life.
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