VII.4.3 Electric actuator

Electric actuators can be of the following forms: Electric current/voltage, Solenoid, Stepping Motor and DC/AC Motor.

Current or voltage can easily be regulated to adjust the flow of energy into the process, e.g. heater, fan speed regulator etc . Energy supplied by the heater element is , where current, resistance, time of heating. The current/voltage can be regulated using

Fig. VII.13: A schematic of Rheostat

potentiometer (or rheostat), amplifier or a switch.

A rheostat is a device that has variable resistance to current flow (Fig. VII.13). The current flowing through the circuit is , where can be varied by suitably sliding the pointer. The power transmitted to the heater would be . As the pointer slides towards a lesser value of , heater receives more power for heating.