How Does an Ammeter Differ from a Voltmeter?
The Difference Between Ammeter And Voltmeter is a fundamental concept in mathematics and physics, vital for understanding how electrical measurements are made in circuits. Examining these instruments helps students differentiate between current and voltage measurements, enhancing clarity in circuit analysis for board exams and competitive tests like JEE.
Mathematical Meaning of Ammeter
An ammeter is a specialized instrument used to measure the electric current flowing through a conductor or circuit. It provides readings in amperes, allowing precise quantitative analysis of current magnitude.
The ammeter must always be connected in series so that the total circuit current passes through the device, enabling direct measurement without circuit deviation.
Ammeters possess very low resistance, ensuring minimal voltage drop and preventing alteration of the current to be measured.
Understanding Voltmeter in Mathematics
A voltmeter measures the potential difference, commonly called voltage, between two points in an electrical circuit. Its unit of measurement is the volt, indicating the energy per unit charge transferred between those points.
Unlike the ammeter, the voltmeter is always connected in parallel across the component or segment where voltage is to be measured. This configuration allows comparison between two potential points without altering the main current flow. Its high internal resistance minimizes circuit disturbance.
For other types of potential-measuring devices, refer to Difference Between Cell Potential And EMF.
Difference Between Ammeter and Voltmeter: Comparison Table
| Ammeter | Voltmeter |
|---|---|
| Measures electric current in a circuit | Measures voltage between two points |
| Unit is ampere (A) | Unit is volt (V) |
| Connected in series with circuit component | Connected in parallel across component |
| Has very low resistance | Has very high resistance |
| Minimizes voltage drop across itself | Minimizes current drawn through itself |
| Symbol is “A” in circuit diagrams | Symbol is “V” in circuit diagrams |
| Ideal value of resistance is zero | Ideal value of resistance is infinite |
| Does not measure potential difference | Does not measure current |
| Current to be measured flows through the ammeter | Only a negligible current passes through voltmeter |
| Used for current calculations and circuit troubleshooting | Used for voltage verification and analysis |
| Accuracy increases with lower resistance design | Accuracy increases with higher resistance design |
| Can be analogue (pointer) or digital (display) | Available in analogue or digital form |
| Indispensable for measuring series currents | Essential for measuring parallel voltages |
| Current divides after passing through ammeter | Voltage is sampled across two points simultaneously |
| Placement affects full circuit’s current flow | Placement does not affect main circuit current |
| Sometimes constructed from a modified galvanometer | Can also be constructed from galvanometer by adding resistance |
| Preferred in current intensity measurements | Preferred in potential drop studies |
| Used in combination with shunt resistors | Utilizes large series resistance for accuracy |
| Detects faults by identifying excess current | Detects faults by verifying expected voltages |
| Integral for safety checks in circuits | Integral for ensuring voltage supply stability |
Important Differences
- Ammeter measures current, voltmeter measures voltage
- Ammeter has low resistance, voltmeter has high resistance
- Ammeter connects in series, voltmeter connects in parallel
- Ammeter’s ideal resistance is zero, voltmeter’s is infinite
- Ammeter reading is in amperes, voltmeter in volts
- Incorrect connection can damage both instruments
Simple Numerical Examples
If 2 amperes of current flows through a resistor and an ammeter is placed in series, it shows 2 A. If a voltmeter is connected across a 5 Ω resistor carrying the same current, it reads:
$V = IR = 2 \times 5 = 10~\text{V}$
This demonstrates direct current measurement by the ammeter and voltage drop calculation by the voltmeter.
For application-based examples, see the Difference Between Ammeter And Voltmeter resource.
Where These Concepts Are Used
- Circuit analysis and fault detection
- Testing household and industrial electrical systems
- Physics and electronics laboratory experiments
- Ensuring safety in electrical appliance servicing
- Calibration and maintenance of electrical equipment
- Educational demonstrations and practicals
Concise Comparison
In simple words, an ammeter measures electric current in series, whereas a voltmeter measures potential difference in parallel.
FAQs on Difference Between Ammeter and Voltmeter Made Easy
1. What is the main difference between an ammeter and a voltmeter?
An ammeter measures electric current while a voltmeter measures electric potential difference (voltage).
Key differences include:
- Ammeter: Connects in series with the circuit, measures current in amperes (A)
- Voltmeter: Connects in parallel with the circuit component, measures voltage in volts (V)
- The internal resistance of an ammeter is very low, while that of a voltmeter is very high
2. How do you connect an ammeter and a voltmeter in a circuit?
An ammeter is always connected in series, while a voltmeter is connected in parallel to the circuit element.
- Ammeter: Series connection with the component whose current is to be measured
- Voltmeter: Parallel connection across the component whose voltage is to be measured
3. Why should an ammeter have low resistance and a voltmeter have high resistance?
An ammeter must have low resistance to avoid altering the current in the circuit, whereas a voltmeter needs high resistance so it does not draw extra current.
- Low resistance in ammeter prevents voltage drop
- High resistance in voltmeter avoids circuit loading
4. Can a voltmeter be used as an ammeter or vice versa?
No, a voltmeter cannot be used as an ammeter and vice versa due to the difference in their internal resistance and intended connections.
If interchanged, it can:
- Damage the instrument
- Give incorrect readings
- Affect the circuit performance
5. What are the similarities between an ammeter and a voltmeter?
Both ammeter and voltmeter are instruments used to measure electrical quantities in a circuit.
Similarities include:
- Both are measuring instruments
- Both have marked scales and pointers
- Both work using similar principles of electromagnetic deflection
6. What precautions should be taken while using ammeter and voltmeter?
Precautions ensure safety and accurate readings when using ammeter and voltmeter.
Key precautions:
- Never connect an ammeter in parallel
- Never connect a voltmeter in series
- Ensure ranges are suitable for circuit values
- Check for zero error before use
- Connect observing correct polarity
7. What happens if an ammeter is connected in parallel?
If an ammeter is connected in parallel, it may get damaged due to its low resistance, causing a large current to flow through it.
Possible outcomes:
- Instrument damage
- Irregular current flow in the circuit
- Safety risks like sparking
8. State one use each of ammeter and voltmeter.
An ammeter is used to measure electric current and a voltmeter is used to measure electric potential difference in circuits.
Examples:
- Ammeter: Used in a series circuit to monitor current for physics experiments
- Voltmeter: Used in a parallel circuit to check battery voltage
9. What is the SI unit of current measured by an ammeter and voltage measured by a voltmeter?
The SI unit of current is ampere (A) and the SI unit of voltage is volt (V).
- Ammeter: Measures current in amperes (A)
- Voltmeter: Measures voltage in volts (V)
10. What is the working principle of an ammeter and voltmeter?
Both ammeter and voltmeter work on the principle of deflection of a pointer due to magnetic effect of electric current.
Key points:
- Based on moving-coil galvanometer principle
- Pointer deflection proportional to measured quantity
- Calibration adjusts scale for current (ammeter) or voltage (voltmeter)
