A galvanometer of resistance G is shunted by resistance S. What series resistance must be added so that the total main-circuit current remains unchanged?
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A galvanometer of resistance G is shunted by resistance S. What series resistance must be added so that the total main-circuit current remains unchanged?

G1 Physics · Accepted Answer

Step 1: Initially, the galvanometer offers resistance G. Step 2: After adding a shunt S, its parallel equivalent resistance becomes R_parallel = GS/(G+S). Step 3: To keep the main-circuit current unchanged, external series resistance must restore the original total resistance G. Step 4: R_series = G − GS/(G+S) = G²/(G+S). Final answer: (C) G²/(S + G).