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Ohm’s law & power
Current and power dissipation in a resistor.
HB3YAQ · Ajdin HadzicLearning to take awayhttps://hb3yaq.ch/en/tools/ohms-law
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Formula & context
I = U/R; P = U · I = U²/R
An ideal resistor relates voltage and current linearly. Absorbed electrical power is dissipated as heat.
A worked example
12 V across 100 Ω gives 0.12 A and 1.44 W. A resistor rated at 0.25 W would be undersized.
Assumptions & limits
Applies to DC or RMS values across a purely resistive load. RF impedance, resistance changes with temperature and component ratings are not calculated.
Volts, amperes, ohms and wattsUnderstand the reasoning →From reading to experimenting
Ohm’s law & power
12 V across 100 Ω gives 0.12 A and 1.44 W. A resistor rated at 0.25 W would be undersized.
Open example with starting values →Voltage: 12 V · Resistance: 100 ΩBack to the learning article →Then change exactly one value. Compare the result and use the formula to explain why it changes. The model limits below the calculator also apply here.