P2.3.1 Static Electricity
P2 Physics
KS4 ADDITIONAL SCIENCEMr D Powell
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Connection
• Connect your learning to the content of the lesson
• Share the process by which the learning will actually take place
• Explore the outcomes of the learning, emphasising why this will be beneficial for the learner
Demonstration
• Use formative feedback – Assessment for Learning
• Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex
• Offer different ways for the students to demonstrate their understanding
• Allow the students to “show off” their learning
Activation
• Construct problem-solving challenges for the students
• Use a multi-sensory approach – VAK• Promote a language of learning to
enable the students to talk about their progress or obstacles to it
• Learning as an active process, so the students aren’t passive receptors
Consolidation
• Structure active reflection on the lesson content and the process of learning
• Seek transfer between “subjects”• Review the learning from this lesson and
preview the learning for the next• Promote ways in which the students will
remember• A “news broadcast” approach to learning
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P2.3.1 Static Electricity
a) When certain insulating materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one material and onto the other.
b) The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
c) When two electrically charged objects are brought together they exert a force on each other.
d) Two objects that carry the same type of charge repel. Two objects that carry different types of charge attract.
e) Electrical charges can move easily through some substances, eg metals.
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What is the title of the lesson... S
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Atoms & Ion theory..... TThe protons and neutrons make up the nucleus of the atom. Electrons move about in the space round the nucleus.
1. A proton has a positive charge.2. An electron has an equal negative charge.3. A neutron is uncharged.
An uncharged atom has equal numbers of electrons and protons. Only electrons can be transferred to or from an atom.
Adding electrons to an uncharged atom makes it a negative ion (because the atom then has more electrons than protons).
Removing electrons from an uncharged atom makes it a positive ion (because the atom has fewer electrons than protons).
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Charging of Insulators P There is a big difference between a conductor and an insulator.
Insulators can carry a charge and their structure does not allow electrons to flow freely.
Conductors allow electrons to freely pass through them and cannot keep a static charge.
TASK: Try out these experiments as shown. Also try out bending a stream of water with your plastic ruler. Now write up your findings!
HSW: Can you deduce anything special about the charges on specific rods
Type of Rod Black Clear Milky White
Black Nill Repel Attract
Clear Repel Attract
Milky White Repel
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“An electric discovery”
1. Why did scientists conclude from these results that there are only two types of charge?
2. In terms of electrons, explain why equal and opposite amounts of charge cancel each other out.
What does the word ‘charge’ mean? Someone who runs at top speed ‘charges along’ filled with adrenalin. An electrically charged object is filled with static electricity. The term ‘electric charge’ was first used over 300 years ago when scientists discovered that certain materials such as ebonite, glass and resin attracted bits of paper when they are rubbed. They knew this effect had been discovered by the ancient Greeks using amber, a naturally occurring fossil resin. So they used the word ‘electric’, from the Greek word for ‘amber’, to describe the attractive power of these materials. The action of rubbing a suitable material was said to charge it with electricity. Further experiments showed that:
identical charged materials always repel each other, ebonite and glass attract, ebonite and resin repel, glass and resin attract.
More tests showed that there are two types of charge and they cancel eachother out. So the two types of charge were called ‘positive’ and ‘negative’.
H
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Summary Questions PWhen a polythene rod is charged using a dry cloth, it becomes negative because it …… electrons that transfer from the ……….. to the …………
When a perspex rod is charged using a dry cloth, it becomes positive because it …… electrons that transfer from the……….. to the …………
When rubbed with a dry cloth, perspex becomes positively charged. Polythene and ebonite become negatively charged. State whether or not attraction or repulsion takes place when:
1. perspex rod is held near a polythene rod,
2. a perspex rod is held near an ebonite rod,
3. a polythene rod is held near an ebonite rod.
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Van De Graaff Generator MThe Van de Graaff generator charges up because:
1. the belt rubs against a comb and becomes charged,
2. the belt carries the charge onto an insulated metal dome,
3. sparks are produced when the dome can no longer hold any more charge.
The charges are in fact “static electrons” which have been pulled up from atoms in the Earth and sit on the dome.
The movement of the charges means that we now refer to this as an “electrical current”.
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Can you remember... S1. Last lesson we talked about three
particles that a atom is made up from. Can you remember the names of each?
2. charge on each?
3. Define an “ion” when compared to an “atom”?
4. How you give an atom a static charge?
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Dangerous Sparks... MThunderclouds gain a separation of charges by ice crystals rubbing together inside the cloud. In the end the bottom of the cloud gains a negative charge and finally when the difference in charge or “potential difference” gets too much between it and the ground a large number of electrons flow to Earth. This is what we call a lightning strike.
A lightning conductor on a building is very clever as it actually reduces the potential between the cloud and Earth as free electrons in the spike are pushed into ground making the chances of a strike reduce.
However if the charge or “potential difference” gets too much it conducts the strike to the Earth without damaging the building as the electrons are conducted away.
TASK: explain what is a lightning strike and why is it dangerous, how can we reduce the problem?
B/C
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Cool Facts - Extra
A lightning bolt travels at about 14,000mph bringing 300,000 volts of electricity to the ground in just a few milliseconds, and heating up the air around it to 30,000°C
One lightning bolt can reach 30,000°C, five times hotter than the sun. Air can often smell 'burnt' after a lightning strike, as the huge amount of energy released can alter molecules in the air. This heating also causes thunder as the air rapidly expands and then contracts, causing vibrations. These vibrations, or sound waves, we hear as thunder.
As lightning is seen and thunder heard, lightning travels at the speed of light, and thunder at the speed of sound. The difference in these speeds is so great that light could travel right round the world before sound finished the 100m sprint.
This speed difference provides an easy way to see how far away the lightning struck. Count the seconds between the lightning and the thunder, each second represents 300m distance from the thunderstorm. You will be surprised at how often storms that you think are on top of you are quite a long way off.
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Summary Questions... P1) a) An electric current is …… .
b) A metal is a conductor because it contains ……
c) A …… metal object loses electrons when it is connected to the ground.
2)
a) Why can’t we charge a metal object if it is earthed?
b) A drawing pin is fixed to the dome of a Van de Graaff machine with its point in the air. Explain why this stops the dome charging up when themachine is switched on. [Higher]
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Paint Spraying
+++
+ - -
-
--
-
- ---
Paint gunnozzle has apositive charge
+
The nozzle is connected to one terminal of an electrostatic generator.
The other terminal is connected to the metal panel, which is earthed.
Electrostatic Generator
MTask: Can you explain (in
terms of electrons) moving how the process works.
C
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Photocopier 3D Version
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The Photocopier / Laser Printer M
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The Photocopier / Laser Printer functions...
A There is now a copy of the original page.
B A copying plate is electronically charged.
C The paper is heated to make the black powder stick.
D An image of the page you want to copy is projected onto the plate.
E Where light falls on the plate, the electrical charge leaks away.
F The parts of the plate that are still charged attract bits of black powder.
G The black powder is transferred from the plate to a sheet of paper.
MTask: using your diagram
which is now labelled write out numbers 1-7 in your book and sequence the statements in the correct order....
1. B2. D3. E4. F5. G6. C7. A
C
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Electrostatic Smoke Precipitator
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Electrostatic Precipitator M
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Electrostatic Smoke Precipitator functions...
A The waste gases pass by a charged metal grid.
B The particles are attracted to the oppositely charged plates and stick to them.
CThe collecting plates are knocked regularly so
the smoke particles fall down and are removed.
DThe large collecting plates on the precipitator are given an opposite charge to that on the
grid.
E The smoke particles are repelled by the similar charge on the grid.
F The smoke particles pick up an electric charge as the pass through the grid.
G The waste gases are then free of smoke particles.
MTask: using your diagram
which is now labelled write out numbers 1-7 in your book and link the statements in the correct order....
1. A2. F3. E4. D5. B6. C7. G C
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Antistatic Floors
In a hospital, doctors use anesthetic gases during operations. Some of these gases are explosive. (i.e. oxygen)
If the gas escapes into the air, a tiny spark could make it explode.
To eliminate static charge in operating theatres, an antistatic material is used for the floor surface.
This material is a poor electrical insulator so it conducts charge to Earth.
TASK: make a note of this idea in your book. Sequence the text into a flow chart. Then try and relate this to another situation where static might be dangerous.
C/ D
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Powder Tests
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Inkjet Printer
An ink jet printer has an ‘ink gun’ inside that directs a jet of charged ink droplets at the paper. The ink droplets pass between two metal ‘deflecting’ plates before reaching the paper. By making one plate positive and the other negative, the droplets can be deflected as they pass between the plates. This happens because the droplets are attracted to the oppositely charged plate.
The plates are made positive and negative by applying a potential difference to them. The potential difference is controlled by signals from the computer. The computer is programmed to make the inkjet print characters and graphics on the paper at high speed.
Can you construct a short flow chart on how the inkjet printer works.
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Chips!
TASK: A company that makes computers has found that some of its chips don’t work. The supplier says the company must be more careful when the chips are used. Imagine you work in the company. You think the problem is at the supplier, what will you instruct them to do?
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Summary Questions P1 Copy & Complete……
a) Positively charged paint droplets from a paint spray are …….… by the spray nozzle. The droplets ……….…electrons when they reach thenegatively charged metal panel.
b) Dust particles in an electrostatic precipitator touch a positivelycharged wire. The particles …….… electrons to the wire and are then……..… by a negatively charged metal plate.
2)a) The delivery pipe between the road tanker and the storage tank must be earthed before any petrol is pumped from the tanker. Why is this an important safety measure?
b) Why does an operating theatre in a hospital have antistatic floorcovering?
A There is now a copy of the original page.
B A copying plate is electronically charged.
C The paper is heated to make the black powder stick.
D An image of the page you want to copy is projected onto the plate.
E Where light falls on the plate, the electrical charge leaks away.
FThe parts of the plate that are still charged attract bits of black powder.
G The black powder is transferred from the plate to a sheet of paper.
A The waste gases pass by a charged metal grid.
BThe particles are attracted to the oppositely charged plates and stick to them.
CThe collecting plates are knocked regularly so the smoke particles fall down and are removed.
DThe large collecting plates on the precipitator are given an opposite charge to that on the grid.
E The smoke particles are repelled by the similar charge on the grid.
F The smoke particles pick up an electric charge as the pass through the grid.
G The waste gases are then free of smoke particles.
P2.3.1 Static Electricity
a) When certain insulating materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one material and onto the other.
b) The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
c) When two electrically charged objects are brought together they exert a force on each other.
d) Two objects that carry the same type of charge repel. Two objects that carry different types of charge attract.
e) Electrical charges can move easily through some substances, eg metals.
P2.3.1 Static Electricity
a) When certain insulating materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one material and onto the other.
b) The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
c) When two electrically charged objects are brought together they exert a force on each other.
d) Two objects that carry the same type of charge repel. Two objects that carry different types of charge attract.
e) Electrical charges can move easily through some substances, eg metals.
P2.3.1 Static Electricity
a) When certain insulating materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one material and onto the other.
b) The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
c) When two electrically charged objects are brought together they exert a force on each other.
d) Two objects that carry the same type of charge repel. Two objects that carry different types of charge attract.
e) Electrical charges can move easily through some substances, eg metals.
