Final answer:
An ammeter is a device used to measure the flow of electric current in a circuit and must be connected in series with the component being measured. It comes in analog and digital forms, with analog using a galvanometer and a needle display, and digital displaying numerical digits.
Step-by-step explanation:
A device specifically designed to measure current is known as an ammeter. An ammeter must be connected in series with the component whose current you wish to measure. This is because in a series circuit, the same current flows through all components, making it possible for the ammeter to determine the current flow accurately.
There are two types of ammeters commonly used: analog and digital. Analog ammeters use a galvanometer with a needle that moves over a scale. Digital ammeters use an analog-to-digital converter and display the current as numerical digits.
When an ammeter is placed in series in a circuit, regardless of its exact position, it will measure the same current, as long as it's between two points on the same branch of the circuit. For example, whether it is between points d and e or between points f and a in a given circuit, the reading will remain constant. This feature ensures that the ammeter can provide a reliable measurement of the current.