What is the voltage power current and resistance of an electrical heater?

The two most important ratings for an electrical heater are its rated power and its rated voltage, and these will be printed on a 'nameplate' fixed somewhere on the heater (e.g. '3 kW at 230 V').

For the heater to operate at its rated power, it must be subject to its rated voltage. In the above example, the heater will only operate at 3 kW if it is supplied with 230 V.

If you know the heater's power (P) and its voltage (U), then you can calculate the rated current (I) it will draw from the supply, using the equation: I = P/U.

You can also determine its resistance (R), using the equation R = U2/P.