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Difference Between Ammeter and Voltmeter

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Last updated date: 04th Mar 2024
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Ammeter and Voltmeter

Ammeter and voltmeter both devices are used in an electrical circuit to measure different aspects of electricity. Among them, an ammeter gives you the measure of current while the voltmeter helps in calculating the voltage or potential difference between two points in an electric circuit. 


What is Ammeter and Voltmeter?

Ammeter – It is an instrument that is used to measure the current in an electrical circuit. It gets its name from Ampere which is the unit of electric current. 


Applications of an Ammeter:

  • This device is easily available and helps determine the flow of current quite accurately.

  • It can be used both domestically and for industrial purposes. 

  • It is widely used by manufacturing and instrumentation companies.

  • It can be used with a thermocouple to measure temperature.

  • It can be used to check faulty circuits in offices and homes. 

Voltmeter – This instrument measures the voltage between two points in an electrical circuit. It is present in both digital and analogue forms. 


Applications of a Voltmeter

  • A voltmeter is used for a number of purposes even though it is not as accurate as an ammeter.

  • It measures the voltage in a circuit and is also used in both homes and big factories.

  • It proves quite useful in debugging thereby certifying the presence of the optimal value of the required voltage.

  • It can be coupled with cathode ray tubes to ensure the accuracy of the results and measurements taken. 

  • It is also used in labs by young students and scholars for experimenting and testing purposes.


What is the Difference Between Ammeter and Voltmeter? 

There are two ways to measure electricity 

  • Using current 

  • Using voltage

Ammeter and voltmeter are used to measure the flow of current and the measure of voltage, respectively. The significant difference between these two devices lies in their use. Further, look at the table below to understand the difference between an ammeter and a voltmeter. 



Ammeter

Voltmeter

Use

The flow of current is measured using this instrument.

Voltage or potential between two points in an electric circuit is measured using this device.

Connection

The electrical circuit element is connected in series with an ammeter.

The electrical circuit element is connected in parallel mode with a voltmeter.

In Terms of Resistance

The resistance of an ammeter is low so that it does not affect the flow of current in a circuit.

Since it is used to measure the difference in potential between two points, voltmeters have high resistance.

Accuracy of Ammeter and Voltmeter

It measures the flow of current accurately.

It is less accurate with the measurement

Ideal Case

An ideal Ammeter is supposed to have zero resistance, even though it is not practically possible.

In an ideal voltmeter, the current is zero and resistance is infinite. The ideal resistance of voltmeter and ammeter is infinity and zero, respectively.

Representation

‘A’ denotes an ammeter.

‘V’ is used to denote voltmeter.


Mentioned above are a few significant differences between ammeter and voltmeter. Both instruments are present in analogue and digital forms. Analogue meters have a pointer that depicts the measurement whereas digital devices display the value of current or voltage on the screen.  


Galvanometer

We have talked about ammeters and voltmeters but now let’s see what a galvanometer is. It is a device used to detect current flow in a circuit. Current sensitivity is the term used to refer to the current that gives a full-scale deflection of the galvanometer’s needle. Thus, it is the maximum current that the instrument is capable of measuring. A galvanometer can even function as an ammeter or a voltmeter upon making some requisite changes. 


Potentiometer

When we try measuring the EMF of a battery, we generally connect the battery directly to a standard voltmeter as in the case in laboratories. However, this implies that the actual quantity measured by the voltmeter is the terminal voltage V. Voltage is related to the EMF of the battery by the equation V=emf−Ir, where the letter i is used to denote the current that flows in the circuit and r is the internal resistance of the battery. 


A potentiometer is a null measurement device that is also used to measure voltage but in a slightly different manner. A voltage source is connected to a resistor in the circuit, and a constant current is made to pass through it. There is a steady drop in potential along with the wire present. Consequently, a variable potential is obtained through contact along the wire.


Multiple-Choice Questions 

1. Current is measured using _______ by connecting it in _______ with the electric circuit. 

  1. Voltmeter, series

  2. Voltmeter, parallel

  3. Ammeter, series

  4. Ammeter, parallel

Ans: c 


2. Digital meters are preferred over analogue meters. 

  1. True 

  2. False 

Ans: a


3. An ideal voltmeter can be considered as a _________ circuit. 

  1. Power

  2. Infinite 

  3. Short

  4. Open 

Ans: d 


4. An ideal ammeter can be treated as a __________ circuit. 

  1. Open 

  2. Short

  3. Infinite 

  4. Power

Ans: b

FAQs on Difference Between Ammeter and Voltmeter

1. How to connect an ammeter and voltmeter in a circuit? 

Ammeter is connected in series with the circuit element whereas voltmeter is connected in parallel with the electrical circuit element. Both are used as measuring instruments for electrical calculations and can help in various calculations by evaluating the value of current and voltage in a circuit. Circuit diagrams help students in being able to visualise how the entire setup is done. They represent diagrammatically the correct way of connecting these two electrical instruments in a circuit. In addition to this, a galvanometer and a potentiometer can also be added to the circuit. 

2. Why is the ammeter connected in series? 

Ammeter is connected in series to obtain maximum current flow in the electric circuit. This is possible because its internal resistance is very low. Hence, the flow of current in the circuit can be measured with accuracy. Objects connected in series experience the same current flow in a circuit.

3. Why is the voltmeter connected in parallel? 

We have already discussed how and why an ammeter is connected in series in a circuit. In contrast to this, a voltmeter is connected in parallel. If the voltmeter is connected in series with the circuit element, then the potential difference between the two points will be zero because they lie in the same line. Also, the high internal resistance of the voltmeter is used for evaluating the potential difference between the two points. 

4. What is a digital voltmeter?

By now, we all know that there are various types of voltmeters available in the market that are used for different purposes. One such type of voltmeter is the digital voltmeter. Digital voltmeters are instruments that measure the electrical potential difference between two given points in a circuit. The current flowing in the circuit may be alternating current or direct current. There are five functional segments in a digital voltmeter. These components perform the functions of pulse generation, gating, counting clock pulses, analogue to digital conversion, and latching.