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What happens if shunt resistance in ammeter has large value and if resistance connected in series with voltmeter has a low value?

What happens if shunt resistance in ammeter has large value and if resistance connected in series with voltmeter has a low value?

Grade:12

2 Answers

Arun
25750 Points
6 years ago
Dear Yash
 
A galvanometer is calibrated by choosing the correct shunt resistance.   For example, if a galvanometer alone has a full scale sensitivity of 50 micro amperes and you want to make a meter with a full scale sensitivity of 50 milli amperes, you must choose a shunt resistance such that 1/1000 of the current flows in the galvanometer and the other 999/1000 of the current flows in the shunt resistor.  Suppose the galvanometer coil has a resistance of 100 ohms.  This means that when it deflects to full scale (50 micro amperes) it will have 5 millivolts across it.  Now choose the shunt resistance to pass (50 mA - 50 uA) = 49.950 mA when 5 millivolts is applied.  R = V / I so Rshunt = 5 milli volts / 49.950 mA = 100.1001001... ohms.  Now, if the shunt resistance is changed to a smaller value, then more current will flow in the shunt and less in the galvanometer, so the reading will be in error by being too small.  If the shunt resistance is changed to a larger value, then less current will flow in the shunt and more in the galvanometer coil, so the reading will be in error by being too large.  If you open the shunt, you might damage the galvanometer.  If you short the shunt, the galvanometer should read zero.
ChesLans
11 Points
5 years ago
Hi...i am a new user here. As per my knowledge shunt is hooked up into the system so you need to take in account the voltage and dissipate some of the current going through in heat.

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