The resistance of an electrical component is a measure of its opposition to current.

Resistor, variable reistor and ohmmeter symbols

Resistor circuit symbol, a rectangleVariable resistor circuit symbol - a rectangle with an arrow at a 45 degree angle which begins below the rectangle at the left hand side, travels through it, emerging at the top right.Circuit symbol for an ohmmeter - incomplete circle with horizontal feet at bottom point outwards, all enclosed within a complete circle.

A resistor opposes current by converting the electrical energy in a circuit into heat energy.

Variable resistors have many practical applications including volume controls, eg on a radio, and speed controls, eg on a mixer or a drill. There is usually a dial or sliding switch on the variable resistor which rotates or slides