For ammeter shunts. which one of the following is not a possible requirement?

For ammeter shunts. which one of the following is not a possible requirement? Correct Answer It should have high thermal automotive force

Range extension of ammeters:

• Shunts are used for the range extension of ammeters.
• A shunt is a low-value resistance having minimum temperature co-efficient.
• It is connected in parallel with the ammeter whose range is to be extended. The combination is connected in series with the circuit whose current is to be measured.
• Shunt provides a path for extra current as it is connected across (in parallel with) the instrument.
• These shunted instruments can be used to measure currents many times greater than their normal full-scale deflection currents.
• Its resistance should not vary with time.
• It should carry current without excessive temperature rise
• The ratio of maximum current (with shunt) to the full-scale deflection current (without shunt) is known as the ‘multiplying power’ or ‘multiplying factor’ of the shunt.

In the figure

I is total current flowing in the circuit

Ish is the current through the shunt resistor

Rm is the ammeter resistance