What is an Ammeter? Definition and Function

How Does an Ammeter Work?

To learn how does an ammeter work, recall that an ammeter measures the current in an electric circuit through a set of coils with very low resistance and inductive reactance. Once connected in series, the ammeter causes a very small drop in voltage due to its low resistance, allowing the electric current to pass through it and be measured. There are many ammeters to measure direct or alternating current, but all depend on the ammeter having very low internal resistance. Inside the ammeter, there is a shunt connected in parallel to a device called a galvanometer. The shunt is a resistance that allows the measured current to flow through the ammeter and delivers a full reading. The galvanometer is a sensitive current detector. Readings of electric currents in the ammeter are usually given in milliamperes in electric circuits that have batteries as a power source. In alternating current cases, such as at home, an ammeter will read larger values which will be in amperes.

Ammeter parts

What Does an Ammeter Do in a Circuit?

To know what does an ammeter measure recall that the name is made of two parts: ampere and meter, so an ammeter measures amperes or, in other words, electric currents: direct or alternating. An ammeter only measures electric current. To measure an electric current is what is an ammeter used for once connected in series in an electric circuit. To learn what does an ammeter do in a circuit, think about how the electric current flows through the internal parts of the ammeter, causing its needle to deflect and showing the electric current strength in the targeted part of the electric circuit.

Ammeter

Some ammeters are equipped with analog screens. In this case, instead of the needle, the screen shows in digits the electric current strength and the type of current. Therefore, knowing what is an ammeter in a circuit gives access to the electric current strength while never changing the potential difference in the circuit due to its low internal resistance. It is essential to remember that an ammeter must always be connected in series. The very small internal resistance of the ammeter can lead to a short circuit if the ammeter is set up in a parallel connection with the part of the circuit to measure the passing current. So ammeter function is a tool used to measure the current in a circuit while being connected in series with the circuit so that the measured current flows directly through the ammeter. It is important to set up an ammeter correctly - always in series - to measure the current passing through a resistor or any part of the circuit in an electric circuit.

Ammeter in a circuit

In a circuit made of parallel and series circuits, it is vital to learn how to connect the ammeter to measure the electric current. For example, the circuit in the diagram presents a combination of series and parallel circuits in one circuit where four resistors are connected to one source of power or a battery. Two resistors, R1 and R3, are connected in series, and the other two resistors, R2 and R4, are also connected in series. The whole branch of R1 and R3 as a one-piece is connected in parallel with the whole branch of a one-piece of R2 and R4. The two conjunction points to the right and left create the parallel part of the circuit. At any place between the battery and the conjunction point, an ammeter connected in series will read the total current of the circuit. Meaning, connect the ammeter at any point in series between the conjunction point to the left or the connection point to the right and all the way down to the battery, and the ammeter will only read the total current of the circuit that the battery sends to every part of the circuit. But to measure the electric current that passes through a resistor R1 and R3, an ammeter must be connected in series in the space between the resistors or at any point between the resistor R1 and the conjunction point to the left or at any point between the resistor R3 and the conjunction point to the right but never beyond any conjunction point. And similarly, to measure the electric current that passes through a resistor R2 and R4, an ammeter can be connected in series in the space between the resistors or at any point between the resistor R2 and the conjunction point to the left or at any point between the resistor R4 and the conjunction point to the right but never beyond any conjunction point.

Combination of parallel and series electric circuit

Lesson Summary

To know what is ammeter or understand the ammeter definition, remember that the electric current in a circuit is measured in amperes. The device used to measure an electric current in a circuit is called an ampere meter or ammeter. An ammeter is used in series with the part of the circuit to measure the passing current to measure direct or alternating electric current.

An ammeter only measures electric current when it is set up correctly. If the ammeter is wrongly connected -in a parallel connection- that can lead to a short circuit because of its low resistance. To learn how does an ammeter work, recall that an ammeter uses a set of coils to measure the current in an electric circuit. The electric current readings on an ammeter are usually given in milliamperes.