The Types, Working Principles and Uses of a Galvanometer

Working principles and uses of a Galvanometer

A Danish physicist & chemist Hans Christan Ørsted discovered the first instrument to calculate current or create magnetic fields. A French physicist & mathematician André – Marie Ampèré gave a mathematical expression for the discovery of Hans device. In this post, we shall describe the working principles and uses of a galvanometer, the differences it has with the voltmeter and ammeter and the different types of galvanometer used in laboratories and industries.

1. What is a Galvanometer and how does it work
2. Constructing a Galvanometer
3. Working principle of a Galvanometer
4. Applications/ Uses of Galvanometer (See also the Ballistic Galvanometer)
5. Advantages of a Galvanometer
6. Disadvantages of a Galvanometer
7. Ammeter
8. Conversation of a Galvanometer to an Ammeter
9. Differences between a Galvanometer and an Ammeter
10. Voltmeter
11. Conversion of a Galvanometer to an Voltmeter
12. Differences Between a Galvanometer and a Voltmeter
13. Moving coil Galvanometer

 

What is a Galvanometer?

Definition: A Galvanometer is an electromechanical measuring instrument that is used for detecting the presence of small current and voltage.

 

How Does a Galvanometers Work:

A galvanometers works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field.
The early galvanometers made in the 1800’s were uncalibrated but the improved versions now called ammeters are calibrated and could measure the flow of current more precisely.

 

Basic Components of a Galvanometer:

The following are the three main parts of a galvanometer;
1. The moving coil
2. Suspension
3. Permanent or stable magnet

 

 

How to Constructing a Galvanometer:

Construction of ballistic galvanometer

The suspension, moving coil and the permanent or stable magnet are required for the construction of a galvanometer.

 

The Moving Coil:

The moving coil is the current – carrying element present in the galvanometer. It is either circular or rectangular in shape with a no. of twists of copper wire present in it. It moves freely between stable magnetic poles. A low resistance flux lane is given by the iron core and therefore it gives the tough magnetic field for the twist to move.

 

Suspension in a Moving Coil Galvanometer:

Plane ribbon is used when balancing the coil. The ribbon supplies current towards the coil. The lower suspension and the torque effect of the other coil can be negligible.
The upper suspension coil can be designed with a gold or copper wire in the ribbon form.

 

We shall now delve into the working principles and uses of a galvanometer.

 

Working Principles of a Galvanometer:

“When a current carrying coil is placed in the uniform magnetic field, moving coil galvanometer experiences a torque.”

 

Applications / Uses of a Galvanometer:

1. Galvanometers are used in determining current.
2. Galvanometers are used to control systems like lasers.

 

Advantages of a Galvanometer:

1. Galvanometers are not affected by strong magnetic fields.
2. They are accurate.
3. Galvanometer scales are uniform.

 

Disadvantages of a Galvanometer:

1. The temperature change will cause a change within the torque.
2. The restoring torque cannot be changed.
3. They cannot be used for AC quantity measurements.

 

Ammeter:

An ammeter is a measuring instrument. Ammeters are used for measuring direct or alternating electric current.

 

Conversion of a Galvanometer to an Ammeter:

A galvanometer is converted to an ammeter by connecting a low resistance (shunt) in parallel with the galvanometer.

 

Differences between a Galvanometer and an Ammeter:

1. A galvanometer detects the magnitude and direction of small current present in the circuit.
While
Ammeters are used to determine the magnitude of current flowing in a circuit.
2. The accuracy of a galvanometer is less, compared to that of an ammeter.
3. Sensitivity of a galvanometer is more, compared to an ammeter.
4. A galvanometer uses a moving coil which is free to rotate between the permanent magnet.

 

Voltmeter:

Voltmeter is an instrument for measuring voltage or potential difference.

 

How to Convert of Galvanometer to a Voltmeter:

To convert a galvanometer to a voltmeter a high resistance known as “series resistance” is connected to the galvanometer.

 

Difference Between a Galvanometer and a Voltmeter:

Galvanometers moves in response to an electric current.
While
Potential difference (pd) are measured with voltmeter.

 

Moving Coil Galvanometer:

A moving coil galvanometer is an instrument used to measure electric currents.

 

Types of a Moving Coil Galvanometer

1. Suspended Coil Galvanometer:
A suspended coil galvanometer consists of a rectangular coil of thin insulated copper wires with large number of turns.

2. Pivoted Coil or Western Galvanometer:

A pivoted coil or Western galvanometer consists of a thin insulated copper wire wound on an aluminum frame, rotating freely on a vertical axle between cylindrical pole pieces of a permanent horse shoe magnet.

 

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