Question

A galvanometer having a coil resistance of 60 S2
shows full scale deflection when a current of
1.0 A passes through it. It can be converted into
an ammeter to read currents upto 5.0 A by :-
​

Answer 1

Answer:

A galvanometer having a coil resistance of 60 shows full scale deflection when current of 1.0 amp passes through it

To find when can it be converted into an ammeter to read current up to 5.0 amp

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=1.0A×60Ω

⟹V=60V

Let a shunt of resistance (R

s

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

I=5A=I

s

+I

g

V=I

s

R

s

=(I−I

g

)R

s

(I−I

g

)R

s

=I

g

R

g

(5−1)R

s

=60×1

⟹R

s

=15Ω

is the resistance that should be connected in parallel to convert it into an ammeter of range 5A.