Electric Power Formula

Thursday, March 17, 2022

Electric Power Formula

This light bulb is rated at 60 watts,but what does that mean. Let’s take a look at the electric power formula to see what 60 watts represents.

light bulb

Electric power is the rate, at which electrical energy is transferred by an electric circuit.

The formula for electric power is,

Electric Power = Volts x Current and can be written as P = V x I

  • V = voltage
  • I is current intensity

Voltage is what pushes free electrons around a circuit The greater the voltage the greater the current and as voltage decreases the current will also decrease. It is a measure of potential work. In other words, voltage is a measure of how much work can potentially be done

Voltage is measured in volts 

  • A volt is the work required in Joules to move one Coulomb of charge from A to B
  •  It is expressed as 1 Joule/Coulomb
  • In simple terms Voltage is a measure of potential energy.

Ok but what is a Coulomb?

Coulomb is a measure in charge  It is equal to 1/(1.6×10−19) elementary charges which is the charge of a single proton or the negative charge of a single electron.

Another way you can think of a Coulomb is that it is a bag of electrons and each electron has a charge. It takes 6.2415 x 10^18 electrons to make one Coulomb.

Again a Coulomb is a measure of charge.

Current is all about movement. It is measured in amperes and is a measure of 1 Coulomb of charge passing a point in a circuit every second and is written as Coulomb/second.

In other words an amp is 6.24 x 10^18 electrons flowing past a point each second.

A joule of energy is defined as the energy expended by one ampere at one volt, moving in one second. 

So let’s go back to the 60 watt bulb.

A 60 Watt bulb uses 60 Joules of energy each second it is on.


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