Electric power is the rate at which electrical energy is used or converted — measured in watts, and billed to your home in kilowatt-hours.
At the same 220 V, a higher-power appliance simply draws more current: I = P/V = 100 W / 220 V = 0.45 A.
Power is the rate of doing work, or equally, the rate of consuming energy. In an electric circuit, the rate at which electrical energy is dissipated or consumed is the electric power: P = VI.
Using Ohm's law, this can also be written as P = I²R or P = V²/R — three equivalent formulas for the same quantity, useful depending on which values you already know.
The SI unit of electric power is the watt (W) — the power used by a device drawing 1 A of current at a potential difference of 1 V (1 W = 1 V × 1 A). Since a watt is a small unit for everyday appliances, we commonly use the kilowatt (kW), equal to 1000 W.
Since energy is power multiplied by time, the practical unit of electrical energy is the kilowatt-hour (kWh) — commonly called a 'unit' on electricity bills. One kWh is the energy used by a 1000 W appliance running for 1 hour, and equals 3.6 × 10⁶ joules. This — not the watt — is what you're actually billed for every month.
Key exam points
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Electrical Power - Definition, SI Unit, Formulas | Electricity Class 10 Physics Chapter 12 | NCERT · Gurukul by Oswal