Ohm's Law Basics: Voltage, Current, Resistance, and Power
Ohm’s law connects voltage, current, and resistance for ideal resistors. This guide shows the identities our calculators use—and the AC caveats that keep household wiring in electrician territory.
The core identities
V = I·R, I = V/R, R = V/I, and P = V·I = I²·R = V²/R. If any two independent values are known, the others follow for a resistive path.
Not a substitute for code or a license
Educational worksheets help you understand magnitudes. They do not approve a panel upgrade, choose GFCI/AFCI devices, or replace local electrical code.
Quick practice loop
1
Pick what you know
Voltage and resistance, or voltage and power, etc.
2
Solve with the calculator
Open the Ohm’s law worksheet and choose the solve target.
3
Cross-check power
Confirm P matches V·I before sizing anything physical.
When to switch tools
Use watts↔amps for nameplate conversions with power factor, voltage-drop/wire-size for long runs, and home-utilities worksheets when you care about kWh cost instead of circuit current.