Moving-coil galvanometer

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  • #1
phyphysics
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I know that the pointer of the galvanometer makes use of the turning effect to indicate the strength of the current. Say, the pointer is moved to the position of 8mA, if the current is suddenly withdrawn, the pointer would be pointing back to zero. What's the mechanism behind this?
 

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  • #2
Andrew Mason
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phyphysics said:
I know that the pointer of the galvanometer makes use of the turning effect to indicate the strength of the current. Say, the pointer is moved to the position of 8mA, if the current is suddenly withdrawn, the pointer would be pointing back to zero. What's the mechanism behind this?
A coil spring. The angle is proportional to the torque on the spring, which is proportional to the current in the coil.

AM
 
  • #3
phyphysics
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When the current is just switched off, then there is no turning effect on both the hairsprings and the iron cylinder. By inertia, the pointer must still pointing at the original reading, say, 8mA, so how can the pointer be flicked back to zero when the current suddenly drops to 0 ?
 
  • #4
Andrew Mason
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phyphysics said:
When the current is just switched off, then there is no turning effect on both the hairsprings and the iron cylinder. By inertia, the pointer must still pointing at the original reading, say, 8mA, so how can the pointer be flicked back to zero when the current suddenly drops to 0 ?
But as the needle turns the spring stretches. When the current drops to 0 the spring just returns to its equlibrium position (there is probably some kind of damper to slow the return).

AM
 

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