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in moving coil galvanometer, the coil is wound over the mettalic frame in order to make the galvanometer dead beat i.e. on passing current the galvanometer shows a steady deflection without any oscillation. what does dead beat mean? how is the use of mettalic frame related to this?

in moving coil galvanometer, the coil is wound over the mettalic frame in order to make the galvanometer dead beat i.e. on passing current the galvanometer shows a steady deflection without any oscillation.

what does dead beat mean? how is the use of mettalic frame related to this?

Grade:12

1 Answers

SAGAR SINGH - IIT DELHI
879 Points
12 years ago

Dear student,

When a current is passed through the coil in the direction PQRS, then the coil experiences a torque

t = NIBA sina

Since the magnified field is radial the plane of the coil is parallel to the magnetic field such that a = 90o and hence t = NIBA.

The coil rotates and the phosphor bronze strip gets twisted. As a result a restoring torque comes into play trying to restore the coil back to original position.

If f be the twist produced in the strip and C be the restoring torque per unit twist then the restoring torque = Cf.

In equilibrium,

 

torque in moving coil galvanometer

 

where G is the galvanometer constant.

 

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All the best.

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Sagar Singh

B.Tech, IIT Delhi

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