What function does the range select switch serve?

The range select switch is a crucial component in the operation of ammeters and voltmeters as it enables the user to measure different ranges of electrical values. Specifically, the function of the range select switch in the context of measuring current is to allow the user to switch between high and low current ranges.

When measuring current with an ammeter, it is essential to choose the appropriate range to ensure accurate readings and protect the device from damage due to excessive current. For example, by selecting the high range (0-400), the ammeter can accurately measure larger currents without risking overload, while the low range (0-80) is for measuring smaller currents with greater precision. This flexibility is vital in various electrical applications, as it ensures that the measurement device can adapt to different operating conditions effectively.

The other options describe functions that are not related to the purpose of a range select switch in ammeters. Modifying the current output, changing the voltmeter range, or controlling the cooling fan speed does not describe the specific capabilities of a range select switch when used in the context of electrical measurement.