difference between suspended type MCG and pivoted type MCG
Answers
Suspended type MCG or Moving Coil Galvanometer
1. It consists of a rectangular coil of thin insulated copper wires which have a large number of turns.
2. A suspension fibre of phosphor-bronze is used to suspend the coil between the poles of a powerful horseshoe magnet. A spring is attached at the other end of the coil. The current enters through the fibre and leaves through the spring.
3. In order to make it possible to adjust the plane of the coil the upper end of the suspension fibre is connected to a rotating screw head.
4. The magnet produces radial magnetic field because it has cylindrically concave pole-pieces. So when the coil rotates in any position its plane is always parallel to the direction of the magnetic field. It gets deflected when current flows through the coil.
5. A soft iron cylinder is fixed inside the coil in such a way that the coil can rotate freely around the cylinder and between the poles. The soft iron core increases the strength of the radial magnetic field due to high permittivity.
6. A small plane mirror is fixed to the suspension fibre. Along with the lamp and scale arrangement this is used to measure the deflection of the coil.
Pivoted type MCG or Moving Coil Galvanometer
1. A rectangular coil of thin insulated copper wires which have a large number of turns is pivoted between the poles of a powerful horseshoe magnet. There are two supports which are bearing with almost no friction. There is a pivot in the middle of the supports, the coil is mounted on it.
2. The rotation of the coil is controlled by two hairsprings attached one above and one below the coil. The coils are spiralled in opposite directions. The current enters through one coil and leaves through the other coil.
3. A long pointer is attached to the coil. It moves over a graduated scale.
4. The whole thing is fitted in a box which has a window. Deflection can be observed through the window.