ELECTRICAL ENERGY AND POWER

CONTENT

1. Electrical Energy
2. Electrical Power
3. Electric Meter Reading and Billing
4. Fuse and Circuit Breaker

Electrical Energy

If Q coulombs of electricity flows between two points whose potential difference is V volts, then the work done (W) is given by

\(W = QV \\ Joules = Coulomb \times Volts\)

But \(Q = It\)

Substituting \(Q = It; \\ W = (It)V \\ W = IVt\)

Also substituting \(V = IR\) from Ohms law

\(W = I^2Rt\)

Or substituting for \(I = \frac{V}{R} \\ W = \frac{V^2}{R}t\)

Electrical energy \(E = IVt \\ E = I^2Rt \\ E = \frac{V^2}{R}t\)

Electrical Power (P)

Power is defined as the time rate of doing work.

\(Power = \frac{Energy}{Time} \\ Power = \frac{VIt}{t} \\ P = IV \\ P = I^2R \\ I = \frac{V^2}{R} \\ P = \frac{E}{t}\)

Electric Meter Reading and Billing

To measure or read electricity consumed in order to bill the consumer accordingly, the standard unit commonly used is the kilowatt/hour.