AC/DC ohms law

[new guy]

does OHMS LAW apply equally to dc circuits and ac circuits. (ex.) an electric heater with a resistance of 216 ohms in a 480v ac circuit. Is the current draw going to be 2.22 amps? and will the current draw go down as the heater gets hot?

[Robert Reed]

Yes the two provide the same power with equal resistive loads. However the AC voltage must be the RMS value . Easy to compute with a sine wave as simply V p-p / 2.828 or V peak/1.414.
But not so easy with complex waves or irregular waves. The 216 ohms measured- was that cold resistance, if so the resistance will most certainly go higher when stabilized at it normal running temperature. Most heaters have a wattage rating on them which is the HOT wattage dissipated. So a 120 VAC rating fed from the mains will produce the same heat output as it would with 120 DC applied. Of course we are talking strictly resistive loads here.

[jimmy101]

Like Robert said.

For example, a 100W 120 VAC (RMS) incandescent light bulb has a resistance of about 140 ohms at its operting temperture. At room temperature the resistance is more like 10 ohms. (The filament of an incandescent light operates at about 4500F.)

Light bulbs and heaters are, in a sense, rectifiers. Their light / heat output is rectified for an AC input. A 60Hz input blinks / pulses their output at 120 Hz and full rectifies the input wave form.