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Difference Between Ammeter and Galvanometer

Difference Between Ammeter and Galvanometer

Vishal kumarUpdated on 02 Jul 2025, 04:46 PM IST

The article includes answers for what is ammeter, the function of ammeter, use of ammeter, galvanometer, use of a galvanometer, and the difference between galvanometer and ammeter, the difference between galvanometer and voltmeter, and the difference between galvanometer and ohmmeter etc.

Note: Ammeter in Hindi means ऐमीटर, ammeter meaning in Tamil is அம்மீட்டர், conversion of galvanometer into ammeter in Hindi is धारामापी से अमीटर बनाना

Difference Between Ammeter and Galvanometer
Difference Between Ammeter and Galvanometer

What is the function of an ammeter?

A device measuring the electric current in a circuit is called an ammeter. The SI unit of current is ampere. As the device measures current in ampere, it is named an ammeter. The main function of the ammeter is to measure direct or indirect electric current.

Stansi_Ammeter.jpg

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How does ammeter work?

The ammeter measures the electric current through a set of coils with a low value of resistance and inductive reactance. An ammeter is designed with the principle that the resistance and inductive reactance should have a low value. To have the same current throughout, the circuit connection in the ammeter should be in series.

Types of ammeter:

Ammeter is classified into the following types depending on the constructing principle.

  • The permanent magnet moving coil ammeter: In this type, the ammeter is kept in the middle of the pole of a permanent magnet. Here, the magnitude of the current doesn’t affect the deflection in the coil. Direct current is measured by this ammeter.
  • Rectifier type ammeter: Alternating current is measured by this type of ammeter.
  • Moving iron ammeter: Current passing through the coil affects the deflection of the coil. Both direct and alternating current is measured by this ammeter.
  • Electrodynamometer type ammeter: It is more accurate than other types of ammeter. It also measures both the currents.

Depending on the current measurement, the ammeter is divided into further two types. They are AC ammeter and DC ammeter.

What is the use of an ammeter?

Ammeter is used in many sectors.

  • To check the circuit problems, electricians use an ammeter.
  • It is used to examine the temperature in a thermocouple.
  • It measures the electric current produced by the circuit.
  • The proper functioning of electronic devices is checked by an ammeter.

Related Topics Link,

What is a galvanometer?

A device that measures small electric current produced by the deflection of a moving coil is called a galvanometer.

What does a galvanometer do?

The magnetic effect of electric current is the working principle of the galvanometer. A deflection is observed in the galvanometer’s needle if there is a current in the circuit.

Types of galvanometer:

Types of galvanometer comprise:

  • Tangent galvanometer
  • Mirror galvanometer
  • Ballistic galvanometer
  • Astatic galvanometer

What is the reduction factor of the tangent galvanometer?

To generate a specific deflection, the amount of current needed to pass through the galvanometer is called the reduction factor of the tangent galvanometer.

What is the use of a galvanometer?

The galvanometer is used in the following examples:

  • Laser TV, laser displays, laser engraving, etc use galvanometers to manage their systems.
  • The galvanometer is used to measure the condition of hard drives and CD players.

Commonly Asked Questions

Q: Why does an ammeter have low resistance?
A:
An ammeter has low resistance to minimize its impact on the circuit being measured. If an ammeter had high resistance, it would significantly reduce the current flowing through the circuit, leading to inaccurate measurements. The low resistance ensures that the ammeter doesn't alter the circuit's behavior.
Q: What is the role of a shunt in an ammeter?
A:
A shunt is a low-resistance conductor connected in parallel with the ammeter's coil. It allows most of the current to bypass the sensitive galvanometer mechanism, enabling the ammeter to measure much larger currents than the basic galvanometer could handle alone.
Q: How does temperature affect the readings of ammeters and galvanometers?
A:
Temperature changes can affect the resistance of the coil and the strength of the springs in both devices. This can lead to inaccurate readings. High-quality instruments often include temperature compensation mechanisms to minimize these effects.
Q: Why can't a galvanometer measure large currents directly?
A:
A galvanometer is designed to measure very small currents, typically in the microampere or milliampere range. Large currents would generate too much force on the galvanometer's coil, potentially damaging it or causing the pointer to go off-scale.
Q: Can a galvanometer detect AC currents?
A:
A standard moving-coil galvanometer can only detect DC currents. For AC currents, specialized instruments like hot-wire galvanometers or rectifier-type instruments are used. These can respond to the average value of alternating currents.

What is the difference between an ammeter and a galvanometer?

Although both the ammeter and galvanometer measure electric current, they have difference between them. They are,

Ammeter
Galvanometer
An electric device that measures the current is called an ammeter.
A mechanical device that measures the current is called a galvanometer.
In an ammeter, only the magnitude of the current is measured.Both the magnitude and direction of the current are measured by the galvanometer.
Ammeter detects both direct and alternating currents.Galvanometer detects only direct current.
For an ammeter, the magnetic field is not required.The functioning of a galvanometer requires a magnetic field.
Ammeter is connected in series with the circuit directly.Using the potentiometer, the galvanometer measures current.
Ammeter is less sensitive.A galvanometer is more sensitive.
Ammeter is more accurate.A galvanometer is less accurate.

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What is a voltmeter?

In an electric circuit, an instrument calculating the electrical potential difference between two ends is called a voltmeter. It measures voltages in volts. The potential difference of either direct or indirect current is measured by the device.

Types of voltmeter:

Types of voltmeters based on the construction principle are,

  • The permanent magnet moving coil voltmeter
  • Rectifier type voltmeter
  • Induction type voltmeter
  • Electrostatic type voltmeter
  • Electro dynamometer voltmeter
  • Digital voltmeter

What is an Ohmmeter?

A device that is used to measure electrical resistance is called an ohmmeter. As the resistances are measured in ohm units, the instrument is known as an ohmmeter. Ohmmeter circuit can be either parallel or series.

The Ohmmeter consists of a needle, and two test leads. The battery controls the deflection in the needle. At first, the two test leads should be shorted and the resistance value is noted. Then a fixed range is set for the device. The current will be highest when the needle reaches the highest point on the meter scale. Test leads are removed after testing the circuit. Once when the test leads are connected again, the battery is discharged. The rheostat is adjusted when the leads are shorted. Then the test leads will have zero resistance as the needle reaches the lowest position, zero.

NCERT Physics Notes :

Types of Ohmmeter:

Depending on the application, Ohmmeter is divided into three types. They are,

  • Series type Ohmmeter
  • Shunt type Ohmmeter
  • Multiple type Ohmmeter

Application of ohmmeter:

The ohmmeter is applicable in the following fields:

  • To test the electronic component, an ohmmeter is used in electronic labs.
  • The ohmmeter is used to verify the circuit's functioning.
  • For debugging, it is used in small IC’s.

Difference between galvanometer and voltmeter:

Galvanometer and voltmeter differ as follows:

  • A galvanometer measures the current in the circuit while a voltmeter is a device that calculates the electrical potential difference between two ends in a circuit.
  • The direction of current is measured by the galvanometer but the voltmeter doesn’t measure the current only.
  • The functioning of a galvanometer requires a magnetic field whereas a voltmeter doesn’t require a magnetic field.
  • The circuit connection is in series in the case of the galvanometer while it is parallel in the case of the voltmeter.

Difference between galvanometer and ohmmeter:

The difference between galvanometer and ohmmeter are,

  • The galvanometer measures the electric current in the circuit and the ohmmeter measures the electrical resistance.
  • In galvanometer circuit is in series while the ohmmeter circuit is either series or parallel.

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Commonly Asked Questions

Q: What is the main difference between an ammeter and a galvanometer?
A:
The main difference is their purpose and sensitivity. An ammeter is designed to measure electric current in a circuit, while a galvanometer is a more sensitive instrument used to detect and measure very small electric currents. Ammeters are typically used in practical applications, while galvanometers are often used in laboratory settings for precise measurements.
Q: How does the construction of an ammeter differ from a galvanometer?
A:
While both use similar principles, an ammeter is designed to handle larger currents. It typically has a thicker wire in its coil and a stronger spring to counteract the magnetic force. A galvanometer, being more sensitive, uses a thinner wire and a weaker spring to detect smaller currents.
Q: Can a galvanometer be used as an ammeter?
A:
Yes, a galvanometer can be converted into an ammeter by adding a low-resistance shunt in parallel with it. This allows the galvanometer to measure larger currents by diverting most of the current through the shunt, while only a small fraction passes through the galvanometer coil.
Q: What is the working principle of a galvanometer?
A:
A galvanometer works on the principle of electromagnetic induction. When current flows through its coil, it creates a magnetic field that interacts with a permanent magnet. This interaction causes a deflection of the coil, which is proportional to the current flowing through it. The deflection is indicated by a pointer on a scale.
Q: How is an ammeter connected in a circuit?
A:
An ammeter is always connected in series with the component through which the current is to be measured. This ensures that all the current flowing through that part of the circuit passes through the ammeter.

Frequently Asked Questions (FAQs)

Q: How does the "frequency response" of a galvanometer affect its use in AC measurements?
A:
The frequency response determines how accurately the galvanometer can measure alternating currents of different frequencies. Most moving-coil galvanometers have limited high-frequency response due to inertia and inductance, restricting their use to low-frequency AC or DC measurements.
Q: What is the significance of the "current sensitivity" of a galvanometer?
A:
Current sensitivity is the amount of deflection produced by a unit current. Higher sensitivity allows detection of smaller currents but may also make the instrument more susceptible to disturbances.
Q: What is the principle behind a "tangent galvanometer"?
A:
A tangent galvanometer uses a large circular coil and a small compass needle at its center. The tangent of the angle of deflection of the needle is proportional to the current in the coil, hence the name.
Q: How do ammeters achieve different measurement ranges?
A:
Ammeters achieve different ranges by using interchangeable shunts or by having multiple shunts that can be selected with a switch. This allows a single meter movement to measure a wide range of currents.
Q: How does the shape of the pole pieces affect the performance of a moving-coil galvanometer?
A:
The pole pieces are typically shaped to create a radial magnetic field. This ensures that the torque on the coil is proportional to the current regardless of the coil's position, leading to a linear scale.
Q: How do ammeters handle AC measurements differently from DC?
A:
AC ammeters often use rectifiers to convert AC to DC before measurement, or they may use mechanisms that respond to the RMS (Root Mean Square) value of the AC. This is different from DC ammeters which directly measure the steady current.
Q: What is the purpose of a "light-beam galvanometer"?
A:
A light-beam galvanometer uses a mirror attached to the moving coil to reflect a beam of light onto a scale. This amplifies small movements, greatly increasing sensitivity and allowing for precise readings of very small currents.
Q: How does the "control torque" in a galvanometer affect its operation?
A:
The control torque, usually provided by springs, opposes the deflection caused by the current. It ensures that the deflection is proportional to the current and that the pointer returns to zero when no current flows.
Q: What is the difference between a "null" galvanometer and a deflection galvanometer?
A:
A null galvanometer is used to indicate a zero current condition, often in bridge circuits. A deflection galvanometer measures current by the amount of pointer movement. Null types are often more sensitive but don't provide quantitative measurements directly.
Q: How does the "figure of merit" of a galvanometer relate to its use as an ammeter?
A:
The figure of merit (current sensitivity) determines the shunt resistance needed to convert a galvanometer into an ammeter of a specific range. A more sensitive galvanometer (lower figure of merit) allows for a wider range of ammeter scales with the same basic movement.
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