static electricity Flashcards
What is different about the charges on insulating materials?
They are not free to move
How is static electricity formed?
When two insulating materials are rubbed together, electrons can be rubbed off one material and deposited on the other causing charges to build up.
What is charging by friction?
The material that gained electrons becomes negatively charged because electrons have a negative charge. The material that lost these electrons is left positively charged.
In which direction do electrons move between polythene and cloth duster?
Electrons move from the duster to the polythene
In which direction do electrons move between acetate and cloth duster?
Acetate to duster
How does an electrostatic paint sprayer work?
Paint is charged so that the droplets repel each other; this gives a very fine spray. The surface of the object to be painted is given an opposite charge to the paint, which ensures that it attracts the paint droplets
Give a use of static electricity in factories.
Dust precipitators help to remove dust from chimneys and clean the emissions of factories by using static electricity. The negatively charged grid in the chimney makes dust particles negatively charged. The particles are then attracted to positively charged metal plates and form large particles that fall when they are heavy enough or when they are shaken.
Give a use of static electricity in medicine.
A defibrillator produces electrical shocks that make the heart contract when it is placed firmly on a patient’s chest.
Explain how photocopying works.
Charge is built up on the paper where the image will be printed, and the paper is exposed to toner. The toner is attracted to the charged regions and when heated, the toner will melt and solidify onto the paper.
What is sparking?
Sparking is when the air between two objects becomes ionised due to a large voltage.
The ionised air between oppositely charged surfaces can start conducting if the charges become large enough or the distance becomes small enough.
A spark will be discharged between the surfaces of the oppositely charged objects.
What is earthing?
When the excess charge is removed from an object.
How is an object earthed?
The object is connected to the ground using a wire, which will prevent a build-up of charge since the charge will flow through the wire.
Why might there be a fire when refuelling an aeroplane?
Large volumes of fuel pass through the pipes in a short amount of time. The friction causes the fuel and pipes to become electrostatically charged. This could result in sparks and, since fuel is extremely flammable, it could result in fires.
Sparks and fires are prevented by earthing the fuel tank and pipes so charge cannot build up.
