Which of the following statements are true for a galvanometer?
A. A galvanometer is an electromechanical device which can be used for detection of an electric current in a circuit.
B. A galvanometer can be converted into voltmeter by connecting low resistance in a parallel with galvanometer coil.
C. A galvanometer is based on the principle that a current carrying coil when suspended in uniform magnetic field, it experiences a torque.
D. A galvanometer can be converted into ammeter by connecting high resistance in series with galvanometer coil.
E. A galvanometer is a very sensitive device which gives full scale deflection for a current of the order of \( \mu\mathrm{A} \).
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, C and E only
A moving coil galvanometer works on the torque on a current loop in a magnetic field.
(A) A galvanometer is an electromechanical device which can be used for detection of an electric current in a circuit. — Correct. The deflection of the coil shows the current.
(B) A galvanometer can be converted into voltmeter by connecting low resistance in a parallel with galvanometer coil. — Incorrect. A low resistance in parallel makes an ammeter. A voltmeter needs a high resistance in series.
(C) A galvanometer is based on the principle that a current carrying coil when suspended in uniform magnetic field, it experiences a torque. — Correct. The torque \( \tau = NIAB \) is balanced by the restoring torque \( k\phi \), so \( \phi \propto I \).
(D) A galvanometer can be converted into ammeter by connecting high resistance in series with galvanometer coil. — Incorrect. A high series resistance makes a voltmeter. An ammeter needs a low shunt resistance in parallel.
(E) A galvanometer is a very sensitive device which gives full scale deflection for a current of the order of \( \mu\mathrm{A} \). — Correct. It is a very sensitive device.
NCERT (2026-27):
The Moving Coil Galvanometer – “… The galvanometer consists of a coil, with many turns, free to rotate about a fixed axis (Fig. 4.20), in a uniform radial magnetic field.”
The Moving Coil Galvanometer – “… When a current flows through the coil, a torque acts on it.”
The Moving Coil Galvanometer – “… It can be used as a detector to check if a current is flowing in the circuit.”
The Moving Coil Galvanometer – “… (i) Galvanometer is a very sensitive device, it gives a full- scale deflection for a current of the order of µA.”
Summary – “… 11. A moving coil galvanometer can be converted into a ammeter by introducing a shunt resistance rs, of small value in parallel. It can be converted into a voltmeter by introducing a resistance of a large value in series.”