SP11 - Static Electricity ✓
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SP11a - Describe the movement of electrons and the charges involved when you rub an acetate rod with a cloth.
• Both objects start off as neutral. • Electrons move from the acetate rod to the cloth so the acetate rod ends up positive and the cloth ends up negative.
SP11a - Describe the movement of electrons and the charges involved when you rub an polythene rod with a cloth.
• Both objects start off as neutral. • Electrons move to the polythene rod from the cloth so the polythene rod ends up negative and the cloth ends up positive.
SP11a - Describe what will happen when you hang two rods next to each other with: • Positive and positive charges • Positive and negative charges • Negative and negative charges
• Repel • Attract • Repel
SP11a - Explain how charging with induction works. (Use a balloon a jumper and a wall as an example)
• If you rub a balloon against a jumper, the friction causes electrons to transfer from the jumper to the balloon. • The balloon now has a negative charge • When brought close to a wall, the negative charge of the balloon repels the electrons in the wall • The protons are brought closer to the surface of the wall as they are attracted to the balloons negative charge • The balloon is attracted to the positive charge on the surface of the wall causing it to stick • The wall has an induced charge
SP11b - How might you become charged while walking along a carpet?
Friction between your feet and the floor and slight friction between you and the air builds up charges.
SP11b - After gathering charge, how may you become discharged?
• By touching something made of conducting material, the electrons will jump to the object and head to the ground. • You may experience a small electric shock
SP11b - Explain how lightning occurs.
• Static electricity builds up in clouds due to friction between ice and water particles in air currents. • The negatively charged particle move towards the bottom of the cloud. • As the ground is neutral, it is relatively positive to the cloud and so when the charge in the clouds is too great, they jump to the ground to discharge. • This produces a spark which is lightning.
SP11b - How may a tall building protect an area from lightning.
• A tall building may install a lightning conductor. • This would be a metal structure that would be the tallest structure in an area that runs through the centre of the building to the ground. • This means that a cloud will discharge through this which wont affect the surrounding areas.
SP11b - Explain the safety feature that protects airline tankers and aircrafts.
• As high amounts of fuel pass through the nozzle at a fast rate, this build up friction which charges the fuel droplets. • Once they have built up a great charge they want to discharge. • This would create a spark which would light the fuel causing an explosion. • The bonding line is attached which earths the aircraft so that the charge flows through easily to the ground without any spark.
SP11b - Why don’t cars need a bonding line at petrol stations.
The pipes and the car’s tyres earth the car already.
SP11b - Name some uses of static electricity.
• Electrostatic sprays: • Spray paint • Pesticide • Printers • Electrostatic precipitators
SP11b - How do electrostatic sprays work?
The nozzle contains electrodes which negatively charge the spray droplets. This leads to two things: • The like charge between all droplets spread them out • The negative charge attracts to the relatively positive object/crop and then charges it by induction to stick
SP11b - Name some advantages of electrostatic sprays
• Since they spread out there is wide coverage • Since they attach through static induction there is even coverage • Since all the droplets attach, less spray is wasted
SP11c - What is a force field, and what is an electrostatic field?
• A force field is the area around an object in which an object will experience a force and so… • An electrostatic field is the area around an object where a charged object will experience a force
SP11c - What does a negative and a positive point charge diagram look like
• Both are a dot with equally spaced lines originating form the centre. • In a positive one there are arrows away and in a negative one they are towards
SP11c - What will be the difference between two field diagrams if one has a stronger charge
There will be more lines as they will be closer together
SP11c How do you know where the field is strongest?
Where the lines are closest together
SP11c - What are the four rules about field lines?
• Lines never cross • The closer the lines are is where the field is strongest • Start on the positive charge and end on the negative charge • Shows the direction of force on an object
SP11c - What do two oppositely charged parallel plates form?
A uniform parallel electrostatic field
SP11c - If an alpha particle is placed into a uniform parallel field where will it move?
Towards the negatively charged plate.