Ohm's Law Calculator

Ohm's Law applies to ohmic materials - resistors, wires, and simple conductors. It does not directly apply to non-ohmic components like diodes, transistors, or LEDs, which have non-linear voltage-current relationships. For AC circuits with capacitors and inductors, you need to consider impedance instead of simple resistance.

The symbol I comes from the French phrase "intensité du courant" (current intensity), used by André-Marie Ampère in the early 1800s. The unit of current (ampere) is named after him. Voltage (V) and resistance (R) use more intuitive abbreviations.

If resistance approaches zero, current approaches infinity according to I = V/R. This is a short circuit - extremely dangerous as it can cause fires or explosions. Superconductors have zero resistance but require special conditions (extreme cold) and have current limits.

For series resistors: R_total = R1 + R2 + R3 + ... For parallel resistors: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ... Two parallel resistors simplify to: R_total = (R1 × R2) / (R1 + R2). Series increases resistance; parallel decreases it.

For purely resistive AC circuits, yes. But most AC circuits have inductance and capacitance, creating reactance. You then use impedance (Z) instead of resistance: V = I × Z. Impedance combines resistance and reactance and depends on frequency.