A galvanometer has a coil of resistance 200 with a full scale deflection at 20 . The value of resistance to be added to use it as an ammeter of range (0 - 20) mA is :
- 0.40
- 0.10
- 0.20
- 0.50
Answer
(3) 0.20
Solution
A shunt S is joined in parallel, so the galvanometer and the shunt have the same p.d.:
Ig G = (I - Ig)S
S = Ig GI - Ig = 20 10-6 20020 10-3 - 20 10-6
= 4 10-319.98 10-3 0.20
Answer: (3)