= Moving-coil galvanometer
A <moving-coil galvanometer> has a winding that rotates about an axis, a restoring spring, and a pointer or optical readout. In the radial-field construction, a cylindrical iron core and shaped magnetic poles keep the <magnetic field> approximately in the coil's plane as it turns. The resulting <moving-coil galvanometer torque> is nearly independent of the deflection <angle>; the spring then converts <electric current> into a proportional settled deflection. <Physics Part I, Class XII/Moving Charges and Magnetism>[Physics Part I, Class XII, §4.10, printed pp. 129–130, Figure 4.20 and equation (4.26): radial field, iron core, spring and pointer]{ref}
\Image[/galvanometer-radial-field-coil-torque.png]
{title=Radial gap field and the force couple on a moving coil}
{id=galvanometer-radial-field-coil-torque}
{description=Original top-view schematic: the active wire lengths run perpendicular to the page. Dots indicate outward <conventional current>, crosses inward <conventional current>. Blue arrows show the local <magnetic field>; red arrows show the <magnetic force on a current-carrying wire>. Their <force couple> turns the coil counterclockwise for the illustrated positive <electric current>; the spring supplies the opposite <torque>. Only the working gaps are shown, not the complete <magnetic field lines>.}
{source=galvanometer-radial-field-coil-torque.py}
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