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Electrical safety in labs

Discussion in 'Science' started by Roboteer, Nov 11, 2011.

  1. Roboteer

    Roboteer New commenter

    Hi all,
    I was wondering if anyone knew of a good video that shows the consequences of sticking things into electrical sockets. I have had a look on Youtube but everything I find is either American and aimed at industry or people making light of it. I need something appropriate for secondary pupils.
    Can I also ask whether any of you have any socket covers or other safety devices on the electrical sockets located on the lab benches i.e. within easy reach of pupils?
    Due to an incident we are reviewing electrical safety with our pupils but also wondering whether there are any further steps we can take to make things safer.
    Thanks as ever,
  2. Once in 36y of teaching physics in 3 comprehensive schools (I'll repeat that: ONCE) I had a pupil who deliberately short-circuited a socket and switched on (I was out of the room at the time: sackable offence these days?).
    There was a h**l of a bang (I heard it and ran back in) and the circuit-breaker in the prep room cut off the power instantly. He must have known what he was doing (top set) but perhaps not the consequences (or was he just an inquisitive scientist: to be encouraged?[​IMG]
    The electricity board used to issue a DVD called "Don't Let Him Die" (I think) which was a drama about gangs hanging around in sub-stations, so not quite what you want. However, it used to really hold my Y10 & Y11s attention, even though it was dated and somewhat amateurish. At the end of the drama was a re-issue of the old (b&w) 1minute TV adverts in which youths climb pylons or carry fishing rods near overhead wires, etc.
    IF you are totally worried, film the effect of short-circuiting a socket yourself! DISCLAIMER: NO RESPONSIBILITY ACCEPTED FOR ANYONE CARRYING OUT THIS ACTIVITY. IF your lab-safety devices are good enough and you take appropriate precautions, there shouldn't be a problem; IF they aren't good enough it's better to know now.
    We used to connect a "dead" 240V supply to each end of a sausage using optics pins, THEN switch on. DISCLAIMER: NO RESPONSIBILITY ACCEPTED FOR ANYONE CARRYING OUT THIS ACTIVITY. Obviously, we took great pains to make the system SAFE by having insulated stands, safety screens and a large distance between the pupils and the equipment. The effect was quite dramatic, but that was before H&S got into the act.
    IF you choose to do anything like this, please ensure you are fully aware of YOUR responsibilities. INFORM your line-manager before starting. PRACTICE before involving pupils. You MAY be committing a criminal offence if you carry out any of these activities on school premises.

  3. MarkS

    MarkS New commenter

    Having just searched Youtube, there are some videos of bloody idiots shocking each other using the mains...showing is probably going to make certain types of kids even more likely to try it...
    My suggestion is just to tell classes at the start of each year how dangerous mains electricity is...and leave the rest to their imagination!
    P.S. sorry if my first post sounded stroppy...long day/week!
  4. Roboteer

    Roboteer New commenter

    Sorry for the delay in replying.
    I think I will try to contact the electricity companies and see if they have any materials available.
    Not sure I fancy trying your ideas Physics_Suits_You - with the state of our school buildings not sure I would have any confidence in not ending up dead. For example, in the incident the child received an electric shock from the mains but the trip switch for the lab did not go!
    Don't worry Mark - we all have days like that! I quite fancy the padded cell for myself at the moment!
  5. Without being rude, what are your qualifications in electrical safety, and what is your role in the school?
    A trip switch could easily be just like a fuse ie it will require 30 or 40 or more amps (measure of current) to "trip" and cut off the power. A person has a very high resistance, so 230V will only drive a very small current through them BUT 100mA ie 0.1A will probably kill you. "Trip switches" are there to protect the wires and the building! [​IMG]
    What I would hope you will have, and if you haven't it shouldn't be to expensive to get, is a residual current breaker (rcb). Electric current flows into your room via the live wire and back via the neutral (or in the opposite direction as the ac changes). An rcb detects the fact that these 2 values are the same ("current in a series circuit" - Y8); if there is a difference (possibly as low as 30mA) it will switch off the power. That is what you need to protect people! [​IMG] Why didn't yours work? They should be checked regularly and there should be a written record (UK).
    Obviously, all of this should be dealt with by qualified people. From your comments, I would be getting my Union Rep involved and refusing to work in the room (school?) if it wasn't sorted immediately. If that sounds drastic, so is death.
  6. blazer

    blazer Star commenter

    Likewise in 20 odd years I can only recall one incident and that was when I was on teaching practice. Not my lesson I hasten to add. A pupil in a lesson being covered by a supply teacher pushed bits of his metal pen into a bench socket then shorted them. There was an almighty bang as the circuit breaker cut in, the big metal cover on the circuit breaker box fell off with a huge clang. The teacher screamed, the kids screamed (except for the one with the pen who was stunned). All the teachers, me included, ran into the lab to find the teacher on the floor a total basket case and the kids in hysterics.

    The kid was excluded an the teacher taken home!

    In our labs all the circuits have RCD 'fuses' which will cut out so quickly that you cannot get a fatal shock (not that would like to test that out)!
  7. I usually just tell them about the kid who had burns up his arms and a pair of scissors melted to him when he shoved a pair of scissors into the socket and blew all the power in the science wing. No he didn't die, no his scars weren't that bad, but they might have been. etc etc. (Not me, but a colleague's lesson and it was a stupid child).

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