The original dimmer type that diverted current used a/an:

The original dimmer type that diverted current used a variable resistor. This is because variable resistors, such as rheostats or potentiometers, can adjust the flow of current by changing their resistance. In the context of lighting, increasing the resistance decreases the amount of current flowing through the light bulb, resulting in a dimming effect. This method is based on the principle of resistive heating, where the resistor dissipates energy as heat.

Variable resistors were commonly used in early dimmer designs due to their simplicity and effectiveness in providing a basic level of dimming control. While modern dimmers have evolved to use more advanced technologies, such as transistors and solid-state devices for efficiency, the foundational principle of adjusting current flow to achieve dimming remains relevant.