Bloody Electrostatics demonstrations

Got up at 6:30 this morning to be in school at 7:15 to have lots of time to prepare for a form 5 class on electrostatics which I wanted to film.
Now I’m not normally this dedicated, but because it was being videod (‘videoed’?) I wanted to get everything right.
Electrostatics is dodgy at the best of times, but at half eight this morning every thing was going like a dream. To such an extent that I started wondering why other teachers made such a big deal of it. Maybe they should prepare more – like I was doing.

Class began at about 12 o clock. I started the video, and spent the first ten minutes correcting homework on the board, then started into the demos.
Not one worked as well as it did in the morning.
Some didn’t work at all.
It was baffling, frustrating and funny in roughly equal measures.

I take that back.
Mostly it was frustrating, especially since I had prepared it so well.
The smug factor had felt good too.

It’s possible that atmospheric conditions had changed over a few hours, but I suspect one other variable was that the classroom had had four sets of students sit in there for forty minutes at a time, each breathing in nice clean dry air, and breathing out air which contained a higher percentage of water. As one of the students said: “Come on now sir, I know you blame us for everything else, but you can’t seriously think you can blame us for this one.”
tomorrow I repeat the process first thing in the morning, then again a few hours later, and if the same thing happens I think I might use hot plates or bunsen burners to dry out the air for a spell and then repeat (what happens the water / water vapour when the air drys? Where does it go?).
Edge of the seat stuff this . . .


Horrible Experiments

There are four mandatory experiments to do with Heat on the leaving cert syllabus.
And we always do them.
And, apart from the first, they can all give horrible (and I mean horrible) answers.

I warn the troops in advance and suggest that a percentage of under 30% would be acceptable. It’s not unusual for a student to get a percentage error greater than 100%.
But they generally don’t calculate this untill they are writing up the experiment at home.
They don’t ask about it in class because they probably think that they would just be highlighting their own incompetence, and I don’t mention it because I also am a little embarassed by their results, knowing that they were only following my instructions.

Am I the only teacher who is this inept?
Do many others check?
What do I know? As I keep saying, in this business once we close that classroom door we become kings of our own classroom, and it wouldn’t be unusual for a teacher to go from their own secondary school as a student, up until the day they retire, having only ever seen one other person (their old science teacher) teach any given topic.
This can’t be right.
Can it?