Lesson 1: Electricity 1 Thomas Edison 1847-1931. Lesson Objectives I know what happens when materials are rubbed together. T know what us transferred.

Thomas Edison 1847-1931

Question:

Why does a balloon, when rubbed, stick to a wall or ceiling?

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Other tricks:

1. Bending water2. Attracting paper3. Van de Graff

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Static Electricity

Can build up in our bodies, on us on a dry winters day. We can then feel/see a spark

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Brainiac 38:44 – 44:00 

Recap - Draw the structure of the atom

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What are the charges on the sub-atomic particles?

Protons have positive charge (+)

Neutrons have NO charge

Electrons have a negative charge (-)

Recap – How are IONS formed?

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Negative IONS – gain an electron (gain a negative charge)

Positive IONS – lose an electron (lose a negative charge)

Friction

This causes electrons to move.

Try:• Polythene• Perspex• Glass

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• Rub Polythene with dry clothElectrons move TO the rod so it becomes negatively

charged.

• Rub Perspex with a dry clothElectrons move FROM to rod so it becomes positively

charged.

• Rub Glass with a dry clothElectrons move FROM to rod so it becomes positively

charged.

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Attract or repel

Which attract and which repel?

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Polythene Perspex Glass

Polythene

Perspex

Glass

Repel Attract Attract

Attract Repel Repel

Attract Repel Repel

Negative PositivePositive

Negative

Positive

Positive

Charges on the move.

Electricity can flow in wires.

The rate of flow of electrons is called current.

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Conductors

Metals are good at conducting electricity because they have free (delocalised) electrons.

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Why is it safer to stay inside a car in a thunder storm?

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Charging a Conductor

Lightening is looking for the quickest route to the ground.

Some objects have a wire which enables the current to flow to earth quickly – the object is said to be earthed.

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Franklin – Kite Flying Myth

How does it work?

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Electrons are transferred to the belt (becomes negatively charged)

Electrons are transferred to the dome (becomes negatively charged)

The charge builds up – we say the dome is has more potential energy (more potential difference – voltage)

Uses of electrostatics (p164/5)

Research the following uses/dangers:

• Electrostatic paint sprayer• Photocopier• Tanker problems• Antistatic floors

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Van de Graff generatorsA charge builds up on the dome due to electrons being “______ off” by the belt. If a big enough ______ is built up then the voltage becomes high enough to _____ the air molecules and the electrons “___” down to Earth – this is an electric _________.

Words – charge, jump, current, rubbed, ionise

Use of static 1 - PhotocopiersPhotocopiers use static electricity. They work by: 1) Copying an ______ of the page onto a ______ plate, 2) Light then causes the charge to ____ away, leaving an “electrostatic impression” of the page, 3) The charges left on the plate ______ small drops of black powder, 4) The powder is transferred from the plate onto the _____, 5) The paper is _____ to “fix” the powder.

Words – heated, leak, paper, image, charged, attract

Use of static 2 - Printers

Inkjet printers work by spraying charged drops of ink onto a page. The droplets can be directed using two oppositely charged plates. The voltage on these plates can be easily swapped or varied. The inkjet cartridge can also moved across the page by the printer

Dangers of staticDuring refuelling the fuel gains electrons from the pipe, making the pipe positive and the fuel negative. The resulting voltage may cause a spark – bad news!

Solution: Either earth the fuel tank with a copper rod or connect the tanker to the plane by a copper conductor.

ElectrolysisElectrolysis is used to extract a HIGHLY REACTIVE metal.

= chloride ion

= copper ion

When we electrolysed copper chloride the negative chloride ions moved to the

positive electrode and the positive copper ions moved to the negative

electrode – OPPOSITES ATTRACT!!!

Some example questions1) A current of 2A flows through some copper chloride for 1

minute and 0.01g of copper is deposited at the negative electrode.

a) How much would be deposited if the current was increased to 6A?

b) How much would be deposited if the current was kept at 6A and the experiment was left for another minute?

c) How much charge flowed in question (b) above?

2) A current of 0.05A flows through some copper chloride for 500 seconds and 0.05g of chlorine is released at the positive electrode.

a) How much would be deposited if the current was increased to 0.1A?

b) How much would be deposited if the current was kept at 0.1A and the experiment was left for 250 seconds instead?

c) How much charge flowed in question (b) above?

Are you now able to….

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.