Why is the coil of a ballistic galvanometer wound on a non- metallic f...
The coil of ma ballistic galvanometer is wound on a nonmagnetic former in order to minimise damping when high resistance is connected in series.
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Why is the coil of a ballistic galvanometer wound on a non- metallic f...
Reason for winding the coil on a non-metallic former in ballistic galvanometer
- Definition of ballistic galvanometer: A ballistic galvanometer is an instrument used to measure the quantity of charge passed through a circuit over a short period, i.e., the impulse of current.
- Principle of ballistic galvanometer: The principle of a ballistic galvanometer is based on the fact that the deflection produced by a current impulse in the coil of the galvanometer is proportional to the total charge that passes through it.
- Damping in a galvanometer: Damping refers to the reduction of oscillation in a galvanometer's coil. It is necessary to damp the galvanometer's oscillation to obtain accurate readings.
- Non-metallic former: The coil in a ballistic galvanometer is wound on a non-metallic former, such as a cardboard tube or a plastic bobbin. This is because metallic formers induce eddy currents in the coil, which cause damping.
- High resistance in series: When a high resistance is connected in series with the galvanometer, the damping effect is reduced. This is because the high resistance slows down the current flow, which reduces the induced eddy currents in the coil.
- Minimizing damping: The non-metallic former minimizes the damping effect caused by the induced eddy currents. This allows the galvanometer to respond quickly to the current impulse, producing a greater deflection and a more accurate reading.
- Maximized damping: Using a metallic former would maximize the damping effect, leading to slower response times and less accurate readings.
- High resistance in parallel: Connecting a high resistance in parallel with the galvanometer increases the damping effect. This is because the high resistance provides an alternate path for the current, which reduces the current flow through the galvanometer's coil.
In conclusion, the coil in a ballistic galvanometer is wound on a non-metallic former to minimize the damping effect caused by induced eddy currents, allowing for accurate readings when a high resistance is connected in series.
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