Science Questions

My Dad always used to unplug the TV when lightning was nearby, was this the right thing to do? And, if you'll excuse the pun, Watt is the Current advice? Clive Wilkins, Sutton Coldfield

John Hammond, Met Office:
On average in the UK itself we have about 1 in 3,000,000 people that are struck by lightning so that’s quite a high number.  Most of those do survive but overall the people who have been struck have been doing anything from literally using electrical appliances.  We’ve had accounts of people who’ve been ironing and they’ve been blown across the room because the lightning has come down that particular way.  If you are concerned then I would certainly try and unplug an electrical appliance to try and break that link where the lightning therefore can’t go and not make contact with the ground ultimately.

Dr Bob Howlett, Reader in Electrical and Electronic Engineering, University of Brighton:
Whether you plug your television in or not when there’s lightning around – it’s an interesting question.  I think it’s one of those questions where the answer really is, it doesn’t make too much difference.  It certainly doesn’t make any difference as to whether you get struck by lightning or not because that is down to the distribution of charge in the clouds and the distribution of charge over the nearby buildings and would you believe, the shape of the building: whether there are sharp points on it and things like that.  One little television aerial isn’t going to make any difference that way.  If you do get struck by lightning the current will come down the aerial cable and if your television’s plugged in it may be a good thing because the television will melt down and absorb the energy.  The bad thing is that the cathode ray tube may explode which is not very nice but the television would act like a nice little fuse and absorb some of the energy.  If it’s not plugged in the energy’s going to go somewhere else.  There will be a spark from the plug to the nearest earth point which might be a radiator or it might be you or your dog walking past or whatever but you don’t know what. 

Even if nothing happens to the television aerial the wet walls will be quite good electrical conductors.  You’ll get quite large current coming down the walls on the outside of the building.  Those changing currents will cause magnetic fields, which in turn will induce EMFs or voltages in what could be any electrical equipment in the house.  I’m afraid the answer is there’s probably not much you can do about it apart from lying back and watching the show.

April 2008