I am a graduate student in math in my final year, and for several years have been teaching at my department as a lecturer. This semester, in the same lecture hall there is another lecture that starts 20 minutes after my class ends. It's taught by another instructor from my department. I usually have many students coming to office hours and there are also students asking questions immediately after lecture. Due to other activities, I cannot have office hours right after the lecture this semester and can only stay for about 15 minutes to answer questions.

Many times in the past I had a similar situation and never had any issues with it. This semester the instructor who is teaching right after often arrives 20-15 minutes before her class starts and tells me immediately that I have to go with my students somewhere else. 

I make sure to leave the blackboard clean and take all my stuff away from the instructor's desk before she arrives, but I do believe that I have a right to stay in the classroom after my lecture for at least 5-10 minutes. There is no vacant classroom around, and I don't have time to go with students to my office, which is in a different building.

Last time the instructor told me in front of my students that I don't understand "simple things" and that I am "playing games". When I was talking to one of my students, she stood very close to us and clearly demonstrated that she wanted us out. I tried to explain her that I couldn't go anywhere else due to my time constraints, but she didn't want to listen to me. I really don't understand what "simple" things she meant and what "games" I am playing. 

We leave the board clean. She doesn't need to set up a projector. She can still talk to her students before her class starts, if she wants to (even though it seems like her students don't ask her any questions before their class). So, I don't see how I cause any disruption. 

I had met this woman many times before this semester, but we never talked. I didn't see her talking to other instructors/students much, and she seems to be quite reserved and a bit neurotic. She doesn't want to have any conversation with me regarding the issue.

I felt really offended after last class when she said those things to me in front of my students. What would you do in my case? 

Added later: There are no official rules regarding classroom occupancy between classes. Instructors are supposed to use common sense and be reasonable. For me using 50% of the break time seems reasonable to answer questions after lecture seems reasonable. I agree that for some people it may not.

I don't block the entrance to the classroom. A few students from the next class who come earlier always go ahead and take their seats as soon as my students start leaving the room. I also had one of the students from the next class listening to my explanation to one of those after-class questions and asking me further questions before their class (which is the same class as I am teaching, just a different section). Maybe the instructor got jealous, I don't know.

The entrance to the classroom is from its front (not back), so I do stay in the front. But it is a big lecture hall, and there is a plenty of space in front of the room (the board itself consists of 8 huge panels).

Also, during my career as a grad.student who is also teaching for the department, I have had several observations from experienced professors who are considered to be great teachers at the department and are in charge of undergraduate teaching policy. In my evaluations the fact that there are always several students approaching me with questions after class considered as very positive, meaning that students find me approachable. 

Thank you everyone for answers. 


Question: What to look (out) for when buying a (second-hand) electronic drum kit?
Answer: This Really Depends on the quality of the electronic drum kit your are buying, the thing you should look out for the most is how responsive the heads and cymbals are. I've plaid some shoddy electric kits in my time where it is delayed from the time you hit the pad to the sound playing it is very minute, the timing delay but for a drummer, the timing needs to be perfect or you risk going out of time with the song and so forth when in practice. Also there are naturally things an acoustic kit can do that an electric kit cant, like choking cymbals and performing rim hits. 

The most obvious of differences between Acoustic and electric is the time in which it takes to set up as well as the space in which it takes up. also you wont annoy your neighbours quite as much with electric. But you get a much more authentic and better quality sound from acoustic. the maintenance of an acoustic set requires ALOT more attention. But the cost of electricity is increased with electric. Overall Acoustic is a lot more expensive. the sticks wont degrade half as quickly with electric sets and the heads arguably last longer than the skins for acoustic heads.

If you are buying second hand check the quality of the wires as they can stop the drums working completely. each head has a separate wire. Also pay very close attention to the sensitivity of the foot pedals I once tested a kit that doubled and even tripled up strokes on the hi hit foot pedal so when I pressed the pedal once it hit twice and three times and wouldn't clamp down as a closed hi hat. the springs also in the foot pedals need to be checked for rust and so on. Do not be fobbed off with faulty equipment, test it fully before buying it. things are easily covered up with electric drum kits in my opinion.

I am editing as things spring to my mind here  but also do not leave either kit (Acoustic or Electric) in damp areas, it can take no time at all in killing either. the wires and electronics are a lot more susceptible to damage than on a good hardy shell of an acoustic with its metal stands and clamps but springs in the adjusters of the acoustic kit can also rust making it a pain to adjust them. plastic makes the electric kit easier to adjust and set up.