A galvanometer of resistance 25 Ω gives full-scale deflection at 10 mA. It is used as a multirange ammeter: 0–10 A between O and P, 0–1 A between O and Q, and 0–0.1 A between O and R. Find R₁, R₂ and R₃.

Question

G1 Physics · Accepted Answer

Use the Ayrton-shunt relations for the three ranges with galvanometer resistance 25 Ω and full-scale current 10 mA. Solving the three range equations gives R₁=0.0278 Ω, R₂=0.25 Ω and R₃=2.5 Ω. Hence A.