Moving-Coil Galvanometer

Also called

moving coil galvanometer · galvanometer · torque on a current loop · radial magnetic field · NIAB · current sensitivity · voltage sensitivity · hairspring · soft iron core · pole pieces · ammeter · shunt resistance · voltmeter · series resistance · conversion of galvanometer · धारामापी · अमीटर · वोल्टमीटर · शंट

Topics

• A moving-coil galvanometer is a rectangular coil pivoted in a radial magnetic field around a soft-iron core.
• A current I in a coil of N turns and area A feels a torque NIAB; the radial field keeps it the same at every angle.
• A spring supplies a restoring torque kφ, so the coil turns until NIAB = kφ: the deflection φ is proportional to I.
• Current sensitivity is φ/I = NAB/k; more turns, a stronger field or a softer spring make the meter more sensitive.
• A galvanometer becomes an ammeter when a small shunt resistance is connected in parallel with its coil.
• Most of the current passes through the shunt, so the coil sees only a known fraction and the meter can read amperes.
• A galvanometer becomes a voltmeter when a large resistance is connected in series with its coil.
• The series resistance keeps the meter current tiny, so connecting it across a component hardly changes the circuit.

About this model

A GLB file of about 279 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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