Final answer:
A variable resistor or potentiometer is used as a voltage divider, providing an adjustable voltage output by moving the wiper along the resistive element. It is commonly utilized in electronic circuits to control various functionalities, like the speed of windshield wipers.
Step-by-step explanation:
A variable resistor, often known as a potentiometer, is a three-terminal device that can be used as a voltage divider. When connected to a voltage source, a potentiometer allows for an adjustable voltage output by sliding the wiper along a resistive element. This variable output is used to control different aspects of electronic circuits, like the intermittent speed of windshield wipers. One terminal of the potentiometer is connected to a sliding or rotating contact known as the "wiper", which can be moved to tap into different parts of the resistive element, thereby obtaining a variable resistance or voltage output.
Resistors wired in series are often used as voltage dividers, where the total voltage across all the resistors is divided among them proportionally to their resistances. In contrast, a bleeder resistor, which is typically of a much higher resistance than the circuit it is protecting, ensures the discharge of stored energy from capacitors in power supplies to prevent shock hazards when the apparatus is off.