## Moving Coil Galvanometer – Class 12 | Chapter – 4 | Physics Short Notes Series PDF for NEET & JEE

Moving Coil Galvanometer: A moving coil galvanometer is a type of device that is used to measure electric currents. It works by using the interaction between a current-carrying coil and a magnetic field to produce a rotational force, which can be used to measure the magnitude of the current.

## Moving Coil Galvanometer

A moving coil galvanometer consists of a coil of wire that is suspended between the poles of a strong permanent magnet. When a current flows through the coil, it experiences a torque due to the interaction with the magnetic field, which causes the coil to rotate. The angle of rotation is proportional to the magnitude of the current flowing through the coil.

To increase the sensitivity of the device, the coil is often wound with a large number of turns, and the magnetic field is generated by a strong permanent magnet. The coil is also often mounted on a low-friction pivot, which allows it to rotate freely and respond quickly to changes in the current.

Moving coil galvanometers are widely used in a variety of applications, including laboratory experiments, electrical testing and measurement, and industrial control systems. They are known for their high accuracy, sensitivity, and ease of use, making them a popular choice for many applications. ## Working of Moving Coil Galvanometer

A moving coil galvanometer works by converting the magnetic force produced by a current-carrying coil in a magnetic field into a rotational motion. The basic components of a moving coil galvanometer include a coil of wire, a permanent magnet, and a low-friction pivot.

When a current flows through the coil, it experiences a magnetic force due to the interaction with the magnetic field produced by the permanent magnet. The magnetic force produces a torque on the coil, which causes it to rotate about the pivot. The angle of rotation is proportional to the magnitude of the current flowing through the coil.

To increase the sensitivity of the device, the coil is often wound with a large number of turns, and the magnetic field is generated by a strong permanent magnet. The coil is also often mounted on a low-friction pivot, which allows it to rotate freely and respond quickly to changes in the current.

The angle of rotation can be used to determine the magnitude of the current. This is typically done by using a pointer attached to the coil, which points to a scale or a digital display. The scale or display can be calibrated to show the current in units such as Amperes or milliAmperes.

## Applications of Moving Coil Galvanometer

Moving coil galvanometers have a wide range of applications due to their accuracy, sensitivity, and ease of use. Some of the most common applications include:

• Laboratory experiments: Galvanometers are widely used in physics and electrical engineering laboratory experiments to measure small electric currents. They are particularly useful for demonstrating the principles of electromagnetic induction and the interaction between a current-carrying coil and a magnetic field.
• Electrical testing and measurement: Galvanometers are often used in electrical testing and measurement to determine the magnitude of electric currents in various electrical systems. They are particularly useful for measuring small currents in low-voltage circuits.
• Industrial control systems: Galvanometers are used in industrial control systems to monitor and control the flow of electric current in various applications, such as electric motors, generators, and other electrical components.
• Medical equipment: Galvanometers are used in medical equipment, such as electrocardiographs, to measure the electrical activity of the heart.
• Amplifiers: Galvanometers can be used as part of the input stage of amplifiers, where they convert the small electrical signals from the input source into a larger, more easily measurable signal.

## Limitations of Moving Coil Galvanometer

Like all instruments, moving coil galvanometers have some limitations that must be considered when using them. Some of the most significant limitations include:

• Sensitivity: Although moving coil galvanometers are known for their high sensitivity, they can still have difficulty measuring very small currents. In such cases, other types of instruments, such as digital multimeters or Hall effect sensors, may be more suitable.
• Frequency response: Moving coil galvanometers have a limited frequency response, which means that they may not accurately measure rapidly changing currents. This can be a problem in applications where the current being measured is varying rapidly, such as in high-frequency circuits.
• Temperature sensitivity: Moving coil galvanometers are sensitive to temperature changes, which can affect the accuracy of their readings. This can be a problem in applications where the temperature is changing rapidly, or where precise temperature control is required.
• Nonlinearity: Moving coil galvanometers can exhibit nonlinear behavior, which means that the angle of rotation may not be proportional to the magnitude of the current flowing through the coil. This can be a problem in applications where precise linear measurements are required.
• Drift: Over time, moving coil galvanometers can experience drift, which means that the zero reading may change with time. This can be a problem in applications where precise measurements are required over a long period of time.

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