Double the voltage, quadruple the power

For a fixed resistance, power scales with voltage squared — doubling voltage gives four times the power.

Why it works

P = V²/R falls straight out of Ohm’s law. It’s why small voltage changes on heating elements or motors have an outsized effect on power draw.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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How does voltage affect power?

For a fixed resistance, power scales with voltage squared — doubling voltage gives four times the power. P = V²/R falls straight out of Ohm’s law.

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