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Postby TGTS0907129» Ballistic galvanometer

Describe the Ballistic galvanometer


For some purposes (such as measuring quantity of electricity rather than current) galvanometers are designed with the moving coil having a large moment of inertia and a long period. This enables a small quantity of electricity to be discharged through the galvanometer in a time that is small in comparison with the period of the galvanometer. Under these circumstance a deflection is obtained that is proportional to the charge. This follows from the fact that the angular momentum Iω imparted to the coil is given by

When I the moment of inertia of the coil is ω is the angular speed imported to it, L is the torque produced by the current i, K is a constant, and Q is the total charge sent through the coil. As a result of its angular momentum the coil deflects until its kinetic energy of rotation is transferred into the potential energy of the twisted suspension. The deflection s thus produced is therefore proportional to the charge, or

The kb is known as the ballistic constant of the galvanometer. Ballistic galvanometers are useful for the comparison of capacitors.

By TGTT30071258 on 10/26/2015 11:31:26 PM
TGTS0907129 on 10/26/2015 11:22:44 PM

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