Question

In an electric heater 800 W,400V is labelled what is it mean

Answer 1

Answer:

First, in order to have Power = 500W at 250 Volts, we need 2 Amps of current flow. (P = V x I)

Second, in order to have I = 2A with V = 250V, we need R = V/I = 125 Ohms. Same answer as many of the others. But this is true only for the steady state, while the heater element is hot. Before it heats up, the heater element will have a somewhat lower resistance — something like 7 or 8 percent less if we are comparing resistance at room-temperature vs. red-hot glowing temperature. (Resistance increases with temperature.)

Measure the heater element’s resistance with an ohmmeter (while it’s at room/ambient temperature), and you will definitely see less than 125 ohms. This means that it draws more current (and thus more power) while the element heats up to its steady state temperature.

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