Sketch the circuit of basic DC ammeter , derive equation for shunt resistance.

Sketch the circuit of basic DC ammeter , derive equation for shunt resistance.
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1 Answer

Answer :

image

Derivation

The basic movement of dc ammeter circuit consists of D’ Arsonval galvanometer.

• When large current is to be measured then some extra modification is required.

• For measurement of large current by using same movement a shunt resistor is connected as shown in circuit.

• The value of shunt resistor is very small so that most of the current pass through it and only small current allow to pass through the coil.

• The coil winding of basic movement is small and light therefore it carries very small current. 


The voltage across the shunt and movement must be same.

Vsh =Vm

m

IshRsh=ImRm

Rsh=ImRm/Ish

Rsh=ImRm/(I-Im) 

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