A moving coil instrument is used to measure d.c because it indicates the average value.In a.c, the deflecting torque of the instrument reverses if the current reverses and hence the pointer cannot follow the rapid reversals and the deflection corresponds to a mean torque value of zero.so these instruments cannot be used for a.c.
Thursday, January 1, 2015
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Why cannot a moving coil instrument be used in AC circuits ?
A moving coil instrument is used to measure d.c because it indicates the average value.In a.c, the deflecting torque of the instrument reverses if the current reverses and hence the pointer cannot follow the rapid reversals and the deflection corresponds to a mean torque value of zero.so these instruments cannot be used for a.c.
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