What does a microwave's wattage mean, and why is there a turntable?
Wattage is the power output, and it determines how fast food heats. A 1,000W microwave heats roughly twice as fast as a 500W one.
Two figures appear on microwaves and they are different. The output power is what cooks; the input power drawn from the socket is higher, because the magnetron is not perfectly efficient. Recipes and packet instructions refer to output. Domestic microwaves typically range from about 600W to 1,200W.
Why this matters for cooking. Packet instructions specify a wattage — commonly 800W. If your microwave differs, times must be adjusted: a lower-wattage oven needs longer, a higher-wattage one less. A rough conversion is to scale the time inversely with the power ratio.
Power levels are not variable power. A microwave at 50% does not emit half-strength microwaves. It cycles the magnetron on and off, running at full power part of the time. This is why defrosting works — the off periods let heat conduct inward and even out, rather than cooking the outside while the centre stays frozen.
Why the turntable exists. Microwaves fill the cavity with a standing wave pattern, and standing waves have hot spots and cold spots at fixed positions — points of high and low field intensity determined by the cavity dimensions and wavelength. Food sitting still cooks unevenly at those positions, which is the origin of the boiling-edges-frozen-middle problem.
Rotating the food moves it through the pattern so every part passes through hot spots. It is a mechanical solution to a physics problem.
Flatbed microwaves without turntables use a rotating stirrer — a metal fan above or below the cavity that scatters the waves and moves the pattern instead of the food.
Why standing time is part of the instructions: microwaves heat unevenly, and resting lets conduction equalise the temperature. Skipping it is a genuine food safety issue for reheated meals.