School of Physics Lecture Demonstration Manual

Ea-6 The Current Balance (Including the Kelvin Balance)

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011


To demonstrate the current balance; a device for the absolute measurement of current.



Click on pictures to enlarge.

Current Balance Diagram


The apparatus consists of a balance with a fixed coil B and a coil C suspended from one arm of the balance. The current to be measured passes through the coils such that the force is attractive. Balance is restored by the addition of weights to the pan on the other arm.

A Kelvin deci-ampere balance for measurements in the range 1/10 - 1 Ampere is also available.

Safety notes

Electrical safety 


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