How does a galvanometer work?

A galvanometer works by measuring the torque on a coil or magnet in a magnetic field due to an electric current.

A galvanometer is an electromechanical instrument that measures electric current in a circuit. This sensitive device detects the flow of electric charges, with applications in various scientific and industrial domains. In this article, we will explore the working principles and common types of galvanometers.

Working Principle

The galvanometer’s operation is based on the interaction between a magnetic field and an electric current. When an electric current flows through a coil placed in a magnetic field, a torque is exerted on the coil, causing it to rotate. This torque, proportional to the current, allows the galvanometer to measure the magnitude of the current.

Types of Galvanometers

There are two main types of galvanometers: the moving-coil and the moving-magnet galvanometers.

Moving-Coil Galvanometer: This type of galvanometer consists of a coil, suspended between the poles of a permanent magnet. When a current passes through the coil, it experiences a torque that causes it to rotate. A pointer, attached to the coil, moves along a calibrated scale, indicating the current’s magnitude. A hairspring, connected to the coil, generates a counter torque that restores the pointer to its original position when the current is removed. The moving-coil galvanometer is sensitive and is primarily used for measuring small currents.

Moving-Magnet Galvanometer: In this design, a small magnet is attached to a flexible fiber or a pivoted coil. When a current flows through the coil, the magnet experiences a torque that causes it to rotate. Similar to the moving-coil design, a pointer connected to the magnet moves along a calibrated scale, and the instrument can measure larger currents.

Applications

Galvanometers have numerous applications in scientific research, engineering, and industry. Some common uses include:

Measuring small currents in electrical circuits

Detecting the presence of electric charges

Calibrating other measuring instruments

Recording the output of sensors in various fields, such as geophysics and meteorology

Limitations and Alternatives

Although galvanometers are useful for measuring small currents, they may not be ideal for measuring very large currents or for applications requiring high-speed measurements. Alternatives include ammeters and digital multimeters, which offer greater precision and speed in measuring currents across a wider range.

In conclusion, galvanometers are essential tools in the measurement of electric currents, operating on the principle of magnetic field and current interaction. With a variety of applications, they remain indispensable in scientific and industrial settings. However, for specific requirements, alternative instruments may be more suitable.