In electrical engineering, we come across the terms power and energy often. As laymen, we use these terms interchangeably. Are they same or is there a difference? Let us see.
We have seen what is voltage and current.
Voltage or potential difference is the difference in potentials at two points in an electric field. It is the work done in moving a charge from a point of one potential to a point of higher potential. The potential difference between two points is 1 volt when work of 1 joule is done in moving 1 coulomb of charge between these two points.
Current is defined as the rate of flow of charges through a conductor.
Electrical Power
The physics definition of power is that is it the rate of doing work. Here, it also means the rate at which energy is being consumed.
Note: In Physics, the terms “rate of” always stand for a comparison with time, that is, the quantity is divided by time.
This means that Power = Voltage x Current
From Ohm’s law, V = IR or, I = V/R
The SI unit of power is Watt (W). 1 W of power is consumed when work of 1 joule is done in 1 second. Commercial purposes use bigger units such as kilowatt (kW), megawatt (MW), gigawatt (GW).
As we can see from above, 1 watt can be expressed as-
1W = 1 V x 1 A
-or-
1 W = 1 J/1 s
Electrical Energy
Energy is the capacity to do work. Since power is the rate of doing work, we can say power is the rate of energy consumption.
Power = Energy/time
Energy = Power x time
SI unit of energy is joule. 1 J = 1 watt x 1 sec
Commercial unit of energy is kWh or kilowatt-hour
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