Q 12-04-122JEE MainJEE Main 2023 (15 Apr, Shift 1)Medium
For designing a voltmeter of range $50\ \text{V}$ and an ammeter of range $10\ \text{mA}$ using a galvanometer which has a coil of resistance $54\ \Omega$ showing a full scale deflection for $1\ \text{mA}$ as in figure.
(A) for voltmeter $R\approx50\ \text{k}\Omega$
(B) for ammeter $r\approx0.2\ \Omega$
(C) for ammeter $r\approx6\ \Omega$
(D) for voltmeter $R\approx5\ \text{k}\Omega$
(E) for voltmeter $R\approx500\ \Omega$
Choose the correct answer from the options given below:
Answer: (A) (A) and (C)
Voltmeter: $R=\dfrac{V}{I_g}-G=\dfrac{50}{10^{-3}}-54=49946\ \Omega\approx50\ \text{k}\Omega$ (A).
Ammeter: $r=\dfrac{I_gG}{I-I_g}=\dfrac{1\times54}{10-1}=6\ \Omega$ (C).
Solution by Sreeraj P, M.Sc Physics