Current, Voltage and Resistance

Current is the flow of electric charge, measured in amps (A). Voltage is the energy pushing that charge around the circuit, measured in volts (V). Resistance opposes the flow, measured in ohms (Ω).

Ohm's Law

These three are linked by V = I × R (voltage = current × resistance). Increase the resistance in a circuit and, for the same voltage, the current drops.

Series vs parallel

In a series circuit, current is the same everywhere and resistances add up. In a parallel circuit, voltage is the same across each branch, and current splits between them.

Practice

A circuit has a voltage of 12V and resistance of 4Ω. What's the current?