# What is the effect of a triac on a torque/speed curve?

I am trying to understand the impact of a triac based speed control on the torque/speed curve of a motor. For as easy example, let's use a corded drill as an example. If I pull the trigger all the way the motor gets the full waveform and the torque/speed curve will look like a typical universal motor:

(image source)

Now let's say I only squeeze the trigger down 50% so that the waveform now is chopped up by the triac. What happens to that curve?

Another way to ask the question is does a triac change the speed more, the torque more, or both in some proportion?