formula.expert

Ohm's Law

Also known as V = IR · voltage current resistance · E = IR

V=IRV = I R

Worked example: 2 A through 6 Ω → 12 V — press Try an example to run it live, then adjust anything.

Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Try different units for next level excitement!

Here the solver did the work — could you?

Ohm's Law →

Grade 10Grade 10 Science

Ohm's law →

Grade 11Grade 11 Physics

Ohm's Law →

UniversityCircuits & Electrical Power

Test your skills in the Exam Room: new numbers every attempt — free lessons for students, no sign-up, just pure learning. Find 9 more lessons on this formula.

See your Report Card
Compete with your friends
share your results
Learning zone

Ohm's Law explained

IRV

Georg Ohm published this relation in 1827 after painstaking experiments with wires of different lengths and thicknesses — and was initially ridiculed for reducing electricity to arithmetic. The idea is simple: voltage is the electrical push, resistance is the opposition, and current is what results. Double the push and you double the flow; double the opposition and you halve it. A 12 V car battery connected across a 6 Ω lamp drives 12/6 = 2 A through it; swap in a 3 Ω lamp and the current doubles to 4 A.

The law holds for ohmic conductors at constant temperature — metals, resistors, most wiring. Components like diodes, filament bulbs, and thermistors bend the rule because their resistance shifts as they heat up or as voltage changes. The classic V–I–R triangle mnemonic works because every rearrangement here is a single multiplication or division.

Ohm's Law formula

V=IRV = I R
Where
  • VV= Voltage (V)
  • II= Current (A)
  • RR= Resistance (Ω)

Missing one of these? Work it out first, then come back

Part of this formula set

The Ohm's law wheel

4 formulasOhm's law and the three power equations, arranged so that each one omits exactly one of voltage, current, resistance and power.