Ohm's Law Calculator
Voltage
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Current
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Resistance
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Power
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Understanding Ohm's Law: V = I x R
Ohm's Law: Voltage = Current x Resistance. Enter any two values to solve for the third. Power is calculated as P = V x I.
Voltage is electrical pressure (volts), current is charge flow (amperes), resistance opposes flow (ohms), power is energy rate (watts).
Related power formulas: P = V squared/R and P = I squared x R. Derived from combining Ohm's Law with the power equation.
Frequently Asked Questions
What is Ohm's Law?
V = IR. Voltage equals current times resistance. Formulated by Georg Simon Ohm in 1827.
Power from voltage and resistance?
P = V squared / R. 12V across 100 ohms = 1.44W. Also P = I squared x R or P = VI.
AC circuits?
For AC, impedance (Z) replaces resistance. V = IZ. Ohm's Law applies directly to purely resistive AC loads.
Common voltage levels?
DC: 1.5V (AA), 3.3V/5V (logic), 12V (automotive). AC: 120V (US), 230V (Europe/Asia).