Ohm's Law, Series and Parallel Circuits

The physics view of a simple relationship.

For many conductors at constant temperature, current is proportional to the voltage across them. A graph of voltage against current is then a straight line through the origin. Materials that behave this way are called ohmic; a filament lamp and a diode are not.

In a series circuit the same current flows through every part and the resistances add up. In a parallel circuit every branch has the same voltage and the reciprocals of the resistances add up, so the total is always less than the smallest branch.

• Series: same current, voltages share.
• Parallel: same voltage, currents share.
• Household sockets are wired in parallel.

Browse all 50 physics and electronics pages  |  Back to the course index