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Ohm's Law Calculator
Calculate voltage, current, resistance, and power using Ohm's Law. Enter any two values to find the other two.
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📋 Teaching this? There is a lesson plan ready
Ohm's law: voltage, current and resistance — a complete 40-minute plan for physics, with objectives, the misconceptions to watch for, timed stages and an exit ticket.
Students predict what happens to current when resistance doubles, then check against the animated circuit.
How to use Ohm's law
V = I × R. Know any two and the third follows: R = V ÷ I, I = V ÷ R. Power adds a fourth: P = V × I, which is also I²R and V²÷R.
Ohm's law examples
- 12 V, 4 A
- 3 Ω — 48 WA typical car accessory socket load.
- 2 A through 6 Ω
- 12 V — 24 W
- 230 V, 10 Ω
- 23 A — 5,290 WMains voltage: an element this low draws far more than a domestic circuit allows.
- 5 V, 220 Ω
- 0.0227 A (22.7 mA) — 0.11 WThe usual LED series resistor on a 5 V supply.
Related calculators
- Resistor colour code calculator — read the bands, then use them here
- Voltage divider calculator — two resistors splitting a supply
- LED resistor calculator — sizes the series resistor directly
Worked with this calculator's own formula. Change any figure above in the tool to see your own numbers.
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