What is the purpose of a variable resistor (rheostat)?

A variable resistor, commonly known as a rheostat, plays a crucial role in electrical circuits by changing its resistance to control the flow of current. When the resistance is adjusted, it directly affects the amount of current that passes through the circuit, thus allowing for fine control over electrical devices. This capability is fundamental in applications such as dimming lights, adjusting motor speeds, and tuning electronic devices.

In practical terms, as the resistance increases, the current flowing through the circuit decreases, and vice versa. This unique functionality makes it an essential component for regulating power in various electronic applications. The ability to modify resistance allows users to adapt circuit performance based on specific needs, which is why this option accurately describes the purpose of a rheostat.