Atoms contain these, which can be positive or negative.
Charges
Two oppositely charged particles will do this.
Attract
Two like charged particles will do this.
Repel
Symbol and SI unit of Charge
SI unit: Coulombs
The build up of charged particles.
Static Electricity
List ways on how you can prevent an electrostatic shock
- humidifier
- wear non-synthetic materials
- use an earthing strip
Define the mass number and the atomic number
Mass number - no. of protons + neutrons
atomic number - no. of protons
Define Ionisation
This is the process where an atom gains or loses an electron. When this happens, particles become charged
State how materials are charged
by rubbing. Materials will either gain or lose electrons
If two charged objects are brought close together, they will experience a _______? Discuss
Force. Which is either attractive (two unlike charges) or repulsive (unlike charges).
List three dangers of static electricity
- electrostatic shock
- electrostatic spark
- lightning
Explain what is meant by an electric field and where is this found.
Around each charge is what we call an electric field. A positive charge has an electric field that is pointing away from the charge whilst a negative charge has a field pointing into the charge.
This electric field tells us how strong the influence of electric charges is in the space around them. When you have a charged object, it creates an electric field around itself which will cause an invisible force if another charged object is placed in this field.
Force between charged object depends on 2 conditions
- the quantity of charge on object
- the distance between charged objects
The charge on rubbing material is ______ and __________ to the charge on the rubbed object.
The charge on rubbing material is equal and opposite to the charge on the rubbed object.
How can an object be discharged?
By earthing it. This will provide a path for the excess electrons to flow away or for electrons to flow to the conductor. This will cause the conductor to lose its charge and become neutral.
An electrostatic paint sprayer is about to be used to paint a metal object.
Explain the benefits of using this sprayer compared with one that does not charge the paint.
The paint particles have the same charge. Like charges repel so the paint particles repel each other. This means they spread out for a fine mist which gives an even coating on the object.
The metal object has the opposite charge. This means that the paint particles are attracted to the metal object. This means it takes less time to paint the object.
Uncharged paint forms large droplets and runs off the object so this method means less paint is wasted.
Explain why electrostatic repulsion is the only way to identify an unknown type of charge.
When a charged body is brought near an uncharged body, the charged body will induce an opposite charge on the uncharged body. This will lead to attraction between the two bodies.
Although for repulsion, both bodies need to carry same kind of charge which is possible only if they themselves are charged. Hence repulsion is the sure test to find whether an object is charged or not.
Explain the purpose of a lightning conductor.
The conductor which is fixed on the top of the building to protect the buildings from the damage by lightning. The conductor consists of several sharp metal spikes connected to a thick copper strip. The other end of the copper strip is fixed to a metal plate buried inside the ground.
This will protect high buildings from the massive energy surge had the strike come in via wires or pipes
Discuss (using a drawing) what happens to a neutral object when brought close to a negatively charged object.
Charge separation. Free moving electrons of neutral object are repelled and move away to one side of the object (away from charged object). That leaves the neutral object with a positive side and a negative side.
Explain the difference between a conductor, semiconductor and insulator.
Conductor: a material that allows the flow of electric charge since it has free electrons.
Insulator: a material that does not allow the flow of electric charge since it does not have free electrons.
Semi-conductors: intermediate level of conductivity which varies with temperature. (high temp, more conductivity)