In a carbon pile regulator, the series rheostat with the voltage coil adjusts what?

• A. Output voltage
• B. Input power
• C. Armature current
• D. Regulator temperature

Answer: (A)

The regulator’s job is to keep the system voltage steady by controlling the generator’s field current. The voltage-sensing coil monitors the output and drives the series rheostat (the carbon pile) to change how much current flows in the field. When the output voltage climbs above the set value, the coil increases the resistance in the carbon pile, reducing field current and the generator’s EMF, which lowers the voltage. When the voltage drops, resistance decreases, field current rises, and the voltage goes back up. So this rheostat with the voltage coil adjusts the output voltage. It doesn’t directly set input power, armature current, or regulator temperature.