What are the two types of moving coil galvanometer?
2 Answers
Moving coil galvanometers are sensitive devices used to measure electric current by detecting the torque on a coil placed within a magnetic field. They operate based on the interaction between the magnetic field and the electric current flowing through the coil, causing the coil to rotate. There are two primary types of moving coil galvanometers:
### 1. **D'Arsonval Galvanometer**
The D'Arsonval galvanometer, named after the French physicist Jacques-Arsène d'Arsonval, is the most common type of moving coil galvanometer. Here’s how it works and its key features:
- **Construction:**
- It consists of a coil of wire wound around a lightweight frame, suspended in a magnetic field created by permanent magnets.
- The coil is usually pivoted on a jeweled bearing, allowing it to rotate freely.
- A spring is connected to the coil to return it to its original position when the current stops.
- **Operation:**
- When current flows through the coil, it creates a magnetic field around it. This interaction with the external magnetic field generates a torque that causes the coil to rotate.
- The angle of rotation is proportional to the amount of current flowing through the coil.
- A pointer attached to the coil moves over a calibrated scale to indicate the current value.
- **Characteristics:**
- High sensitivity, making it suitable for measuring small currents.
- Generally used in laboratory settings and for low-voltage measurements.
- Can be designed for both AC (Alternating Current) and DC (Direct Current) measurements.
### 2. **Ammeter-type Galvanometer**
This type of galvanometer is specifically designed for measuring direct current and is typically calibrated to read directly in amperes. Here are the details:
- **Construction:**
- Similar to the D'Arsonval type but often features a different arrangement for the coil and may include additional components such as shunt resistors.
- The coil is also suspended in a magnetic field, and it often has a more robust design to handle larger currents.
- **Operation:**
- When current flows through the coil, it generates a magnetic field, causing the coil to rotate.
- The design may include shunt resistors, which allow a fraction of the current to flow through the galvanometer, protecting it from damage when measuring high currents.
- **Characteristics:**
- Provides a direct reading of current in amperes, making it convenient for practical applications.
- Typically less sensitive than the D'Arsonval type, as it is designed for larger currents.
- Commonly used in electrical measurement devices, including multimeters.
### Summary
Both types of moving coil galvanometers operate on the principle of electromagnetic induction, but they are tailored for different applications. The D'Arsonval galvanometer is well-suited for measuring small currents with high sensitivity, while the ammeter-type galvanometer is designed for direct current measurement in larger ranges. Understanding these types allows engineers and technicians to select the appropriate instrument for specific measurement tasks in both laboratory and field settings.
### 1. **D'Arsonval Galvanometer**
The D'Arsonval galvanometer, named after the French physicist Jacques-Arsène d'Arsonval, is the most common type of moving coil galvanometer. Here’s how it works and its key features:
- **Construction:**
- It consists of a coil of wire wound around a lightweight frame, suspended in a magnetic field created by permanent magnets.
- The coil is usually pivoted on a jeweled bearing, allowing it to rotate freely.
- A spring is connected to the coil to return it to its original position when the current stops.
- **Operation:**
- When current flows through the coil, it creates a magnetic field around it. This interaction with the external magnetic field generates a torque that causes the coil to rotate.
- The angle of rotation is proportional to the amount of current flowing through the coil.
- A pointer attached to the coil moves over a calibrated scale to indicate the current value.
- **Characteristics:**
- High sensitivity, making it suitable for measuring small currents.
- Generally used in laboratory settings and for low-voltage measurements.
- Can be designed for both AC (Alternating Current) and DC (Direct Current) measurements.
### 2. **Ammeter-type Galvanometer**
This type of galvanometer is specifically designed for measuring direct current and is typically calibrated to read directly in amperes. Here are the details:
- **Construction:**
- Similar to the D'Arsonval type but often features a different arrangement for the coil and may include additional components such as shunt resistors.
- The coil is also suspended in a magnetic field, and it often has a more robust design to handle larger currents.
- **Operation:**
- When current flows through the coil, it generates a magnetic field, causing the coil to rotate.
- The design may include shunt resistors, which allow a fraction of the current to flow through the galvanometer, protecting it from damage when measuring high currents.
- **Characteristics:**
- Provides a direct reading of current in amperes, making it convenient for practical applications.
- Typically less sensitive than the D'Arsonval type, as it is designed for larger currents.
- Commonly used in electrical measurement devices, including multimeters.
### Summary
Both types of moving coil galvanometers operate on the principle of electromagnetic induction, but they are tailored for different applications. The D'Arsonval galvanometer is well-suited for measuring small currents with high sensitivity, while the ammeter-type galvanometer is designed for direct current measurement in larger ranges. Understanding these types allows engineers and technicians to select the appropriate instrument for specific measurement tasks in both laboratory and field settings.
The two types of moving coil galvanometers are:
1. **Suspended Type Moving Coil Galvanometer**:
- In this type, the coil is suspended between the poles of a magnet by a fine, non-magnetic wire. When current flows through the coil, it experiences a torque due to the magnetic field, causing it to rotate. The rotation is opposed by the restoring torque of the suspension wire, and the angle of rotation is proportional to the current. The deflection is read using a light beam reflected from a mirror attached to the coil.
2. **Pivoted Type Moving Coil Galvanometer**:
- In the pivoted type, the coil is mounted on a pivot or spindle with bearings, allowing it to rotate freely. A lightweight needle or pointer is attached to the coil to indicate the deflection on a calibrated scale. The restoring torque is provided by a spring. This type is mechanically simpler and more commonly used in instruments like analog ammeters and voltmeters.
Both types function based on the principle that a current-carrying coil experiences a torque in a magnetic field, but they differ in how the coil is supported and how the deflection is measured.
1. **Suspended Type Moving Coil Galvanometer**:
- In this type, the coil is suspended between the poles of a magnet by a fine, non-magnetic wire. When current flows through the coil, it experiences a torque due to the magnetic field, causing it to rotate. The rotation is opposed by the restoring torque of the suspension wire, and the angle of rotation is proportional to the current. The deflection is read using a light beam reflected from a mirror attached to the coil.
2. **Pivoted Type Moving Coil Galvanometer**:
- In the pivoted type, the coil is mounted on a pivot or spindle with bearings, allowing it to rotate freely. A lightweight needle or pointer is attached to the coil to indicate the deflection on a calibrated scale. The restoring torque is provided by a spring. This type is mechanically simpler and more commonly used in instruments like analog ammeters and voltmeters.
Both types function based on the principle that a current-carrying coil experiences a torque in a magnetic field, but they differ in how the coil is supported and how the deflection is measured.