Physics - Current Electricity Question with Solution | TestHub

A. For an ammeter, the current $I_g$ flows through the galvanometer and $(I-I_g)$ through the shunt $S$. Since they are in parallel, $I_{g}G=(I-I_g)S$, which gives $S=G{I}_g/(I-I_g)$.

B. For a voltmeter, the galvanometer and series resistance $R_s$ are in series. The total voltage $V=I_g(G+R_s)$, which gives $R_s=V/I_g-G$. C. An ideal ammeter should have zero resistance to measure current without altering the circuit.

D. An ideal voltmeter should have infinite resistance to measure potential difference without drawing any current from the circuit.