A dimmer is a device used to vary the average voltage applied to an instrument's lamp.

As both average voltage have to be zero to satisfy the steady-state conditions we can write, using the last equation:

So the average voltage across L becomes:

The average voltage of the deflection plates is relatively close to ground, because they have to be directly connected to the vertical output stage.

The cells sustain a higher average voltage during discharge compared to alkaline batteries.

Looking at average voltages, the following can be written:

Therefore, the average voltage across the switch is:

As the "on" to "off" ratio is varied to alter the average applied voltage, the speed of the motor varies.

The percentage "on" time multiplied by the supply voltage gives the average voltage applied to the motor.

An output filter is sometimes installed to smooth the average voltage applied to the motor and reduce motor noise.