Resistance: Circuit Devices

Resistor Converts electrical potential energy to some other form of energy All conductors are resistors Variable resistor: a type of resistor whose resistance can be varied, e.g. a rheostat

Rheostat Consists of a high-resistance wire wound around a coil with a sliding contact Used to regulate current by increasing or deceasing the resistance of a circuit (by increasing the length of the wire the current has to travel through)

Ohmeter Used to measure resistance In order to measure the resistance of a component it is removed from the circuit and connected directly to the ohmeter A combination of an ammeter and voltmeter can also measure resistance

This is the circuit symbol for a fixed resistor

This is the circuit symbol for a variable resistor

This is the circuit symbol for an ohmeter

Potential Divider Can be used to split the voltage of a circuit e.g. a Potentiometer

Potentiometer A three-terminal resistor with a sliding contact that forms an adjustable voltage divider A rheostat can be used as a potentiometer

This is the circuit symbol for a potential divider:

Wheatstone Bridge Used to measure the resistance of an unknown resistor More accurate than an ohmeter

   R₁/R₂ =  R₃/R₄

Metre Bridge A type of Wheatstone bridge Two resistors are replaced by a metre-long wire

   R₁/R₂ = l₁/l₂

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