It gets L1 from the motor.
Specifically, L1 goes through one of the centrifugal switches to get to the heater. That’s important, because it means that if the motor doesn’t run, the heater won’t run either.
And finally question 14: How does the dryer start switch make the motor start?
For this one, you have to understand how all the components involved work. None of them are too complicated, and they’ve all been at least touched on before in Fundamentals or earlier in the Advanced Troubleshooting course.
The dryer start switch is a push-to-start switch, meaning it only closes the circuit for as long as it is being pushed by the customer — usually only a second or less.
Combine that with your knowledge of how split phase motors start (review it in Fundamentals if you need) and how centrifugal switches work, and you should be able to visualize how they all work together.
Let me know if you have a clearer idea of how it all works now.