Moving Coil Galvanometer: Overview, Questions, Preparation

Here's an explanation of the moving coil galvanometer:

Basic Structure: A moving coil galvanometer consists of a coil of wire (usually made of copper or aluminium) that is wound around a lightweight, non-magnetic frame. The coil is suspended between the poles of a permanent magnet.

Magnet and Coil Arrangement: The permanent magnet creates a uniform magnetic field within which the coil is positioned. The coil is free to rotate around its axis.

Damping System: To ensure that the coil comes to rest quickly and doesn't oscillate excessively, a damping system is included. This system usually includes a small air vane attached to the coil, which moves through air or oil, providing resistance to the coil's motion.

Connection to the Circuit: The coil is connected to the circuit where the current must be measured. When an electric current flows through the coil, it generates a magnetic field that interacts with the magnetic field of the permanent magnet.

Working Principle: According to Faraday's law of electromagnetic induction, when a coil of wire moves in a magnetic field, an electromotive force (EMF) is induced in the coil. In the case of a moving coil galvanometer, the coil experiences a torque due to the interaction of the two magnetic fields. This torque causes the coil to rotate.

Determination of Current: The angle the coil rotates is proportional to the current passing through it. A scale is attached to the coil, and a pointer is also fixed to the coil. As the coil rotates, the pointer moves along the scale, providing a reading that corresponds to the current passing through the coil.

Measurement Units: The deflection of the pointer can be calibrated to measure the current in amperes (A) or milliamperes (mA) depending on the instrument's design.

Sensitivity: Moving coil galvanometers are highly sensitive instruments and can detect even tiny currents. They are often used for measurements in the microampere (µA) range.

Applications: These galvanometers are used in laboratories and industries for a wide range of applications, including in the measurement of current, and resistance, and as a component in more advanced instruments like ammeters and voltmeters.

It's important to note that moving coil galvanometers are often used as the basis for ammeters and voltmeters, which are instruments used to measure current and voltage, respectively. In these instruments, additional shunt resistors or multipliers are used to convert the galvanometer's current readings into the appropriate units.