A galvanometer of resistance 60Ω shows full-scale deflection when 1.0A passes through it. It is to be converted into an ammeter reading up to 5.0A. Which arrangement is correct?
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Question

A galvanometer of resistance 60Ω shows full-scale deflection when 1.0A passes through it. It is to be converted into an ammeter reading up to 5.0A. Which arrangement is correct?

G1 Physics · Accepted Answer

Step 1: Given galvanometer resistance G=60Ω, full scale I(g)=1.0A, desired ammeter range I=5.0A. Step 2: A low resistance S goes in parallel with the galvanometer; shunt current I(shunt)=I−I(g)=5−1=4A. Step 3: By equal voltages across parallel branches, I(g)G=I(shunt)S ⇒ S=GI(g)/I(shunt)=60×1/4=15Ω. Step 4: Choose D: connect 15Ω in parallel. Final answer: (D) 15Ω in parallel.