Ohms Law
Calculator

Voltage is the electrical potential difference pushing charge through a circuit, current is the rate of flow of that charge, and resistance is how much the circuit material opposes that flow. Ohm's law, V = I × R, ties all three together for simple resistive circuits.

It depends on what's held constant. If the voltage source (like a battery) stays fixed, increasing resistance reduces the current, since less charge can flow through a bigger obstruction. Voltage only drops if the current source is what's fixed instead.

No — it only applies to "ohmic" components, like standard resistors and wires, where resistance stays constant regardless of voltage or current. Components like diodes, transistors, and light bulbs at high temperature are non-ohmic, meaning their resistance changes with operating conditions, so V = I × R doesn't hold as a fixed relationship for them.

This usually means two of the three inputs were swapped, or units weren't consistent — voltage in volts, current in amps, and resistance in ohms. A negative result almost always signals a sign error or a misplaced decimal rather than a real physical answer.

Beyond solving for V, I, or R, it lets you check whether a circuit design is safe — for example, confirming that a given resistor limits current to below a component's rated maximum, or sizing a resistor to produce a specific voltage drop in the circuit.