Power tells us how fast electrical energy is used, in watts (W). Multiply the voltage by the current: P = V × I. A device on 12 V that takes 0.5 A uses 12 × 0.5 = 6 W. Turn it round to find the current: I = P ÷ V. A home appliance on the 230 V mains that takes 2 A uses 460 W — the numbers are only for calculating; mains appliances are plugged in by adults.
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