Which device is commonly shown as a variable resistor to adjust brightness or speed?

Which device is commonly shown as a variable resistor to adjust brightness or speed?

• A. Variable Resistor
• B. Resistor
• C. Thermistor
• D. Transformer

Answer: (A)

When you want to change how bright a light is or how fast a motor runs, you typically vary the current by changing the resistance in the circuit. The component used for this purpose is the variable resistor, often realized as a rheostat or a potentiometer in knob form. By turning the control, you change the resistance, which in turn adjusts the current through the load: higher resistance means less current and dimmer light or slower speed. A fixed resistor stays at one value and cannot be adjusted, a thermistor changes resistance with temperature rather than by user control, and a transformer alters voltage rather than providing a hands-on, variable current control. So the device commonly shown as a variable resistor for brightness or speed control is the variable resistor itself.

When you want to change how bright a light is or how fast a motor runs, you typically vary the current by changing the resistance in the circuit. The component used for this purpose is the variable resistor, often realized as a rheostat or a potentiometer in knob form. By turning the control, you change the resistance, which in turn adjusts the current through the load: higher resistance means less current and dimmer light or slower speed. A fixed resistor stays at one value and cannot be adjusted, a thermistor changes resistance with temperature rather than by user control, and a transformer alters voltage rather than providing a hands-on, variable current control. So the device commonly shown as a variable resistor for brightness or speed control is the variable resistor itself.