Perhaps things are different in electrical engineering, but in math, the chair:
- introduces the speaker, sometimes just saying their name and the title of their talk, sometimes a lengthier introduction ("[speaker] is professor at XYZ University and works on blablabla");
- says "thank you" out loud and starts clapping at the end;
- asks if there are questions or comments from the audience;
- [optional] if the questions are taking too much time, the chair will say something like "we can discuss this more during the break" and go onto the next step;
- once the questions are over, says "let's thank [speaker] again" and starts clapping;
- announces the time of the next talk ("in 10 minutes", "after the break at 10:30"...). Rinse and repeat.
Sometimes the chair will go as far as warning the speaker if the time limit approaches or has passed. An extra task that sometimes pops up is when the organizers want to make an announcement before/after the talk; then the chair will say "[organizer] has an important announcement, please listen". This is pretty much it.
A handy trick is to get the schedule with speakers' names and talks' titles ahead of time. Then you can practice pronouncing speakers' names, and there's no awkward silence while you say "The second speaker this afternoon is [speaker], who will talk about... uh... squints to read the title on the board [title]".
It's also more or less expected for the chair to prepare at least one question about the talk, even a very simple one. This way, if no other member of the audience has any question, then the chair can say "I actually have a question, [insert question]" after the pause that occurs after "any questions?", saving the speaker a bit of embarrassment.