An ammeter has a galvanometer of resistance G. If only 0.2% of the total current flows through the galvanometer, find the equivalent ammeter resistance.
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Question

An ammeter has a galvanometer of resistance G. If only 0.2% of the total current flows through the galvanometer, find the equivalent ammeter resistance.

G1 Physics · Accepted Answer

Step 1: Only 0.2% of main current passes through galvanometer: I(g)/I=0.002. Remaining current in shunt is I(shunt)=0.998I. Step 2: At equal voltage across G and shunt S: I(g) G=I(shunt) S ⇒ S=(0.002/0.998)G=G/499. Step 3: The question asks for resistance of the complete AMMETER, not shunt alone. Therefore R(A)=(G×S)/(G+S)=G/500. Step 4: Correct answer C, G/500, correcting previous A (which referred to shunt). Final answer: (C) G/500.