Shocking and hair-raising – static electricity is a curious phenomenon.
Static electricity is a build-up of electrical charge on objects, often due to friction.
Unlike dynamic electricity, which we use in our homes, static electricity builds on insulators – materials that do not readily conduct an electrical charge.
When the insulator is brought close to an electrical conductor, the charge is neutralised.
The familiar static shock we experience is caused by the neutralisation of charge.
Build-up of charge on an insulator
Charge is neutralised by a conductor
Neutralisation causes a static shock
If static electricity builds it can be as dangerous as dynamic electricity.
This creates an unseen hazard for rescue helicopters.
As the helicopter blades rotate, they rub against minute dust particles in the air.
The dust particles become charged.
The helicopter blades gain electrons, so become negatively charged.
With the helicopter insulated by the surrounding air, the negative charge builds.
The danger comes when rescuers are winched to the ground, or even the deck of a ship.
When their feet touch the earth – the charge – which has now built to dangerous proportions – can be neutralised, resulting in a life-threatening shock.
Luckily, there is a solution.
Terry Short, Winchman, UK - "We attach a static line, which is about 9 feet of wire, sheathed in a plastic coating, for about three quarters of the length. It's attached to the winch hook and the winchman comes down on the winch hook, holding onto the static line. When he gets close to the vessel, or onto the deck, he just touches the deck or the side of the vessel with the static line – the metal bit of the static line – and that discharges all the static electricity from the aircraft."
This leaves the rescue team free to concentrate on the mission in hand.
Static line – neutralises charge from helicopter
Static electricity isn't always so dangerous.
Usually it results in small harmless shocks or makes your hair stand on end!