Q&A for How to Test a Heating Element

Power formula states that P=IV. Ohms law states that V=IR or I=V/R. Substitute V/R for I in the power formula gives us P=V/R*V or V*V/R, so resistance of the element should be the voltage squared divided by the power.

If the resistance is higher than calculated or it's infinite (so the circuit is open), then you can assume that the heating element has gone bad. Same thing applies to the switch - if after setting the switch to the "on" position, the resistance is infinite, then it means that the switch doesn't close the circuit and it's broken.

If your microwave oven quits heating food, it's time for a new microwave oven. There is usually not much else one can do when this happens.

In the USA for example, your everyday, normal household AC Voltage does in fact equal Vrms=120V, and of course 2-phase AV Vrms=240V. The numerical conversion is already built into the standard. You can verify this easily as almost every modern multi-meter reports Vrms, as that is the more useful and informative value as opposed to peak values.