An undergraduate physics experiment to measure the frequency-dependent impedance of inductors using an Anderson bridge.

One of the most accurate ways to measure the impedance of an electrical component is to place it in a bridge that is then balanced. The most familiar bridge in an undergraduate laboratory is the Wheatstone bridge, which can measure resistance to high precision. Other types are however required for reactive components. This paper describes the use of Anderson’s bridge to measure inductance, allowing both the inductance and resistance of different inductors to be determined. The inductors are analysed with different cores: Perspex, copper and steel. Models for the inductance that include the effect of skin depth, winding proximity, eddy currents, and core effects are introduced and compared to measurements in the frequency range from 100 Hz to 100 kHz.