Static Electricity

Question 1

Which materials are good conductors?

Answer 1

• Metals, such as silver, gold, copper and aluminium
• Non-metals such as carbon

Water can also be included due to its impurities but is not a very good conductor

Question 2

Which materials are good insulators?

Answer 2

• Rubber
• Plastics
• Wood
• Glass

Question 3

What happens when you rub two insulators together?

Answer 3

• They become charged
• One object loses electrons and gives it to another object, caused by friction between the two objects
• The object that loses electrons becomes positively charged, and the object which gains electrons becomes negatively charged

Question 4

When do objects attract?

Answer 4

When the charges are opposite

Question 5

When do objects repel?

Answer 5

When the charges are the same

Question 6

What happens when a negatively charged object comes close to a neutrally charged object?

Answer 6

• The electrons in the negatively charged object will repel the electrons in the neutral object, leaving a positively charged surface of the neutral object
• The electrons in the negatively charged object will be attracted to this positively charged surface, meaning the two objects will stick together assuming the electrostatic forces are stronger than the weight of the objects

Question 7

What can static electricity produce which is a hazard?

Answer 7

A spark

Question 8

What causes this spark to be produced?

Answer 8

Friction between two insulators

Question 9

How can this spark be a problem?

Answer 9

• The spark can ignite flammable materials, like fuel, causing a fire or an explosion
• This is common occurence in fuel pipes, where the friction between the fuel and the pipe causes a build up of charge and a potential spark
• However a spark can be produced by anything like wheels on a road, which can also produce a spark and cause problems

Electrocution can also be a risk of electrostatic electricity if somebody comes in direct contact with a charged object

Question 10

How could a dangerous build up of charge be prevented in vehicles like aircrafts?

Answer 10

• Connect the fuel tank to the earth by a bonding line (basically an earth wire)
• This will carry any excess charge away and run it in the earth, removing the risk of sparks

Question 11

How do black and white photocopiers use electrostatic electricity?

Answer 11

• An image of a document is projected onto a positively charged copying plate
• Where light falls onto the plate, the positive charge leaks away (meaning only the thing you want printed is positively charged)
• A negatively charged black toner is applied to the plate, and it will only stick to the positive charged areas meaning it will only stick to the thing you want printed
• It is heated to make it stick, and then turned over to reveal a copy of the document

Question 12

How do insecticide sprayers (or other sprayers) use electrostatic electricity?

Answer 12

• To be efficient, the sprayer must deliver the chemicals in a fine mist
• The insecticide is given a positive charge, so all the particles repel eachother, resulting in a fine mist of insecticide
• They are also attracted to the negative charge of the earth, so all of the earth will be covered and they will fall quicker and not miss/be blown away

All this can be applied to spraying cars, etc.