What is the purpose of a shunt resistor used with an ammeter?

The purpose of a shunt resistor in conjunction with an ammeter is to increase the ampere indicating range of the ammeter. Ammeters have a limited range and can only measure current up to a certain level due to their internal resistance. By using a shunt resistor, which is a low-resistance path, the majority of the current can bypass the ammeter, allowing it to measure higher currents without being damaged or providing inaccurate readings.

When a shunt resistor is placed in parallel with the ammeter, it effectively divides the current between the two paths. The fraction of the current that flows through the ammeter is determined by the ratio of the shunt resistor to the ammeter's internal resistance. This setup allows the ammeter to provide a reading that corresponds to a much higher current than it could measure directly, hence broadening its measuring capability and extending its range.

This fundamental concept is crucial for applications where high currents need to be measured, which is frequent in electrical engineering and various industrial applications.