How Does an Ammeter Differ from a Galvanometer in Function and Use?
Understanding the Difference Between Ammeter and Galvanometer is significant for physics exams as it helps clarify their functions, construction, and usage in electric circuits. This comparison forms a frequent question in competitive exams like JEE and NEET, making detailed conceptual knowledge essential.
Definition of Ammeter
An ammeter is an electrical instrument designed to measure the magnitude of electric current flowing through a circuit, expressed in amperes. It is always connected in series to ensure the entire current passes through it for accurate measurement.
An ammeter is a modified form of a galvanometer, made by connecting a low resistance, known as a shunt, in parallel with the galvanometer coil. This lowers its overall resistance and allows it to measure larger currents. For related instruments, see Difference Between Current And Voltage.
Definition of Galvanometer
A galvanometer is an electromechanical device used to detect and measure small electric currents, often in microamperes or milliamperes. It shows the presence, magnitude, and direction of current by deflection of its pointer.
It operates on the principle that a current-carrying coil placed in a magnetic field experiences a torque, causing the coil and pointer to move. Its high sensitivity makes it ideal for detecting minute currents, commonly seen in Electromagnetic Induction And Alternating Currents experiments.
Difference Table
| Ammeter | Galvanometer |
|---|---|
| Measures electric current in amperes | Detects and measures small currents |
| Always connected in series | Usually connected in series but for detection |
| Very low internal resistance | Relatively high internal resistance |
| Cannot detect direction of current | Indicates direction of current flow |
| Gives direct current readings | Shows deflection proportional to current |
| Used for measuring larger currents | Measures very small currents |
| Scale is graduated in amperes | Scale usually shows divisions, not specific units |
| Accuracy is high for current measurement | Sensitivity is high for small currents |
| Cannot work as a galvanometer | Can be converted to ammeter by adding shunt |
| Presence of shunt resistor always | Shunt is absent by default |
| Pointer shows value in amperes directly | Pointer shows deflection proportional to current |
| Can measure both AC and DC (with modifications) | Primarily used for DC circuits |
| Not used for null point detection | Used in null point detection in bridges |
| Robust construction for higher currents | Delicate construction for sensitivity |
| No indication for current reversal | Indicates direction reversal by pointer movement |
| Generally costlier due to robust build | Relatively less expensive and simple |
| Not ideal for detecting very small currents | Ideally suited for very small currents |
| Constructed for minimal voltage drop | Voltage drop is higher due to higher resistance |
| Used for continuous monitoring of circuit current | Used mainly for detection and measurement |
| Examples: Laboratory and digital ammeters | Examples: Moving coil and tangent galvanometers |
Key Differences
- Ammeter measures large currents in amperes
- Galvanometer detects very small currents
- Ammeter has low internal resistance
- Galvanometer has comparatively high resistance
- Ammeter shows value; galvanometer shows deflection
- Galvanometer can indicate current direction
Examples
If a circuit draws a current of 2 A, an ammeter connected in series will register "2" on its scale. In contrast, a galvanometer attached to a Wheatstone bridge will show a pointer movement if there is a small imbalance current, helping identify the null point. More about their roles can be found in Difference Between Resistance And Impedance.
Applications
- Ammeter is used for current measurement in circuits
- Galvanometer is used in bridge circuits and potentiometers
- Ammeter is vital for electrical maintenance and laboratories
- Galvanometer helps detect current reversal and small current flow
- Ammeter is essential for monitoring electrical devices
- Galvanometer used in precise experimental measurements
One-Line Summary
In simple words, an ammeter measures large current in amperes, whereas a galvanometer detects and measures very small currents in a circuit.
FAQs on What Is the Difference Between Ammeter and Galvanometer?
1. What is the main difference between an ammeter and a galvanometer?
The main difference between an ammeter and a galvanometer is their function and how they measure current.
- Ammeter: Measures the magnitude of electric current in a circuit.
- Galvanometer: Detects and measures small currents and also shows their direction.
Ammeter is used for higher values of current and is always connected in series, while a galvanometer is used for detecting and measuring very small currents, showing both magnitude and direction. Both instruments are essential in understanding electrical circuits during CBSE examinations.
2. How does an ammeter differ from a galvanometer in its construction?
An ammeter is constructed with a low resistance shunt, while a galvanometer is more sensitive and has a higher coil resistance.
- Ammeter: Low resistance, high current carrying capability, always connected in series.
- Galvanometer: High resistance, sensitive to small currents, typically used to measure tiny electrical currents and can show both magnitude and direction.
In CBSE syllabus, understanding construction differences is vital for scoring in physics exams.
3. Why is a shunt used in an ammeter?
A shunt is used in an ammeter to allow most of the current to bypass the sensitive meter coil, protecting it from high current.
- Shunt has low resistance.
- It diverts the majority of current around the galvanometer.
- Ensures accurate current measurement without damaging the instrument.
- This modification turns a galvanometer into an ammeter, a common board practical question.
4. Can a galvanometer be converted into an ammeter?
Yes, a galvanometer can be converted into an ammeter by connecting a low resistance shunt in parallel with it.
- The shunt bypasses excess current.
- Increases the galvanometer's range to measure larger currents.
- Enables accurate quantitative current measurements in series circuits.
This is a frequent exam question based on current electricity concepts.
5. What are the uses of an ammeter and a galvanometer?
An ammeter is used to measure current, while a galvanometer is used to detect small currents.
Uses of ammeter:
- Measuring current flow in electrical circuits
- Used in laboratory and household applications
Uses of galvanometer:
- Detecting tiny currents
- Indicating current direction
- Used in experiments and to check circuit continuity
These points are important for CBSE board practicals and theory.
6. Why can't a galvanometer be used directly to measure large currents?
A galvanometer cannot be used directly to measure large currents because it is highly sensitive and can be damaged by excess current.
- Its coil and mechanism are designed for small current detection.
- Large currents can overheat or break its coil.
- To measure large currents, a shunt is added to convert it into an ammeter.
This concept is emphasized in circuit analysis chapters.
7. In which circuit position should an ammeter be connected and why?
An ammeter must always be connected in series in a circuit to accurately measure the current passing through an element.
- Series connection ensures all current flows through the ammeter.
- Prevents changes to total circuit resistance and keeps measurements accurate.
This is a standard board exam fact for CBSE students.
8. What is the principle of operation of a galvanometer?
A galvanometer operates on the principle that a current-carrying coil experiences a torque in a magnetic field.
- The coil is suspended in a magnetic field.
- When current passes through, it deflects proportionally to current magnitude.
- Used to detect and measure small electronic currents and their direction.
This working principle is part of the CBSE physics magnetism and currents unit.
9. What are the similarities between an ammeter and a galvanometer?
Both ammeter and galvanometer are electrical measuring instruments based on a moving coil mechanism.
- Use a coil suspended in a magnetic field
- Rely on deflection proportional to current
- Fundamental to electrical circuit analysis
- Galvanometer forms the basis for constructing both ammeters and voltmeters
These similarities often appear in board exam short notes.
10. List the key differences between an ammeter and a galvanometer in a table format.
A tabular comparison highlights the key differences between ammeter and galvanometer:
- Ammeter – Measures current magnitude, low resistance, used for large currents, no direction indicated, always in series.
- Galvanometer – Detects small currents, high resistance, used for small currents, shows direction, can be used in bridge circuits.
