Question

a multirange galvanometer has a full scale deflection current of 100 MA and internal resistance of 2000 ohm is used for measuring current of 1A. Calculate the value of shunt required​

Answer 1

galvanometer of 100 resistance gives full scale deflection with 0.01A current

To find the resistance that should be connected convert it into an ammeter of range 10A

Solution:

Galvanometer is a very sensitive instrument therefore it cannot measure heavy currents. In order to convert a Galvanometer into an Ammeter, a very low shunt resistance is connected in parallel to Galvanometer. Value of shunt is so adjusted that most of the current passes through the shunt.

If resistance of galvanometer is R

g

and it gives full-scale deflection when current I

g

is passed through it. Then,

V=I

g

R

g

⟹V=0.01A×100Ω

⟹V=1V

Let a shunt of resistance (R

s

) is connected in parallel to galvanometer. If total current through the circuit is I.

I=10A=I

s

+I

g

V=I

s

R

s

=(I−I

g

)R

s

(I−I

g

)R

s

=I

g

R

g

(10−0.01)R

s

=100×0.01

⟹R

s

=0.1Ω

is the resistance that should be connected in parallel to convert it into an ammeter of range 10A

Answer 2

Answer:

The Ammeter is a measuring instrument used to find the strength of current flowing around an electrical circuit when connected in series with the part of the circuit being measured