How do you show on a circuit diagram that the output on an electrical device can be varied?

To show that the output on an electrical device can be varied on a circuit diagram, you would typically use a variable resistor or potentiometer symbol. This symbol consists of a resistor with an arrow pointing inwards or outwards, indicating that the resistance can be adjusted. By connecting this symbol to the output component in the circuit, you demonstrate that the output can be varied by adjusting the resistance.