Red Seal Instrumentation and Control Technician Practice Exam

What is the role of a variable resistor in a circuit?

1. To store electrical energy

2. To control the flow of current

3. To measure voltage levels

4. To convert energy from one form to another

The correct answer is: To control the flow of current

A variable resistor, commonly known as a potentiometer or rheostat, plays a crucial role in controlling the flow of current in a circuit. By adjusting its resistance, the variable resistor allows for modification of the current that passes through it, enabling finer control over the circuit's performance. This capability is essential in various applications, such as volume controls in audio equipment, light dimmers, and tuning circuits in radios. In practical terms, when the resistance of the variable resistor is increased, the current flowing through the circuit decreases, and conversely, when the resistance is decreased, the current increases. This functionality is vital for managing power distribution within an electrical system and ensuring that other components operate efficiently without being subjected to excessive current levels. The other roles mentioned in the question—storing electrical energy, measuring voltage levels, and converting energy from one form to another—are typically related to capacitors, voltmeters, and energy converters, respectively. These functions are distinct and do not pertain to the fundamental operation of a variable resistor, which centers entirely on the modulation of current flow.