Solution 1: if there is a technician, don’t hesitate to call upon them.
Solution 2: see if you can work around the broken equipment, or have students share.
Solution 3: see if there is another lab section in which the equipment is working, and ask the TA if your students can share
Solution 4: if the experiments aren’t working, get the students to explain why it’s not working, and based on what they learned in the course, what they expect and why.
- This is where practicing the lab before conducting it is really helpful. It's also useful to talk to TAs who have taught the lab before; they can often tell you what problems to expect, and what experiments simply don't work.