Wednesday, January 7, 2015

Permanent magnet moving coil instrument can be used for ..........

Permanent magnet moving coil instrument can be used for ..........

a. ac work only
b. dc work only
c. both dc and ac work
d. none of the above.

Answer: dc work only

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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