Sparks Flashcards
What does an atom consist of?
An atom consists of a small positively charged nucleus surrounded by an equal number of negatively charged electrons.
The law of electric charge states that:
Like charges repel, unlike charges attract.
All electrostatic effects are due:
to the movement of electrons.
What is in a stable atom?
In a stable, neutral atom there are the same amounts of positive and negative charges.
Rubbing polythene rod
When a polythene rod is rubbed with a duster, electricons are transferred from the duster to the polythene, making the polyethene rod negatively charged.
Rubbing acetate rod
When a acetate rod is rubbed with a duster, electrons are transferred from the acetate to the duster, making the acetate rod positively charged.
In general an object has:
- A negative charge due to an excess of electrons
- A positive charge due to a lack of electrons
Ions
Atoms or molecules that have become charged are ions.
Dangers of electrostatic shock
- When flammable gases or vapours are present, or there is a high concentration of oxygen, a spark from static electricity could ignite the gases of vapours and cause an explosion.
- If a person touches something at a high voltage, large amounts of electric charge may flow through their body to earth,
- Even small amounts of charge flowing through the body can be fatal.
When is static electricity a nuisance?
- Dust and dirt particles are attracted to insulators, such as TV screens.
- Clothes made from synthetic fibres often ‘cling’ to eachother and to the body.
Electric shocks can be avoided in the following ways:
- If an object that is likely to become charged is connected to the earth, any build-up of charge would immediately flow down the earth wire.
- In a factory where machinery is at risk of becoming charged, the operator stands on an insulating rubber mat so that charge cannot flow through them to earth.
- Shoes with insulating soles are worn by workers if there is a risk of charge building up so that charge cannot flow through them to eart.
How are fuel tankers connected to an aircraft?
Fuel tankers are connected to an aircraft by a conducting cable during refuelling.
Anti-static spray
Anti-static sprays, liquids and cloths made from conducting materials carry away electric charge. This prevents a build-up of charge.