EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 2-2 Electric Charge

1
EDEXCEL IGCSE / CERTIFICATE IN PHYSICS
2-2Electric Charge

• Edexcel IGCSE Physics pages 66 to 73

Content applying to Triple Science only is shown
in red type on the next slide and is indicated on
subsequent slides by TRIPLE ONLY
June 17th 2012
2
Edexcel Specification

• Section 2 Electricity
• d) Electric charge
• identify common materials which are electrical
  conductors or insulators, including metals and
  plastics
• describe experiments to investigate how
  insulating materials can be charged by friction
• explain that positive and negative electrostatic
  charges are
• produced on materials by the loss and gain of
  electrons
• understand that there are forces of attraction
  between unlike charges and forces of repulsion
  between like charges
• explain electrostatic phenomena in terms of the
  movement of
• electrons
• explain the potential dangers of electrostatic
  charges, eg when fuelling aircraft and tankers
• explain some uses of electrostatic charges, eg in
  photocopiers and inkjet printers.

Red type Triple Science Only
3
Electrical conductors and insulators
Complete the table below

• An electrical conductor is a material through
  which electric current flows easily.
• All metals are conductors.
• Electrical insulators have a very high resistance
  to the flow of electric current.

copper conductor
rubber insulator
steel conductor
mercury conductor
paper insulator
plastic insulator
diamond insulator
graphite conductor
4
Electric charge
TRIPLE ONLY

• Electric charge can be either positive or
  negative.
• In an atom an electron has a negative charge that
  is of the same size as the positive charge of a
  proton.
• Neutrons have no electric charge.
• As an atom has the same number of electrons as
  protons it is uncharged.

5
Static and current electricity
TRIPLE ONLY

• Static electricity describes the situation when
  electric charges remain stationary.
• This occurs best with insulators.
• An electric current occurs when electric charges
  are moving from one place to another.
• This occurs best with conductors.

6
Charging materials using friction
TRIPLE ONLY

• When certain insulating materials are rubbed
  against each other they become electrically
  charged.
• Electrons are rubbed off one material onto the
  other.
• The material that gains electrons becomes
  negatively charged.
• The material that loses electrons is left with an
  equal positive charge.

7
Force and charge
TRIPLE ONLY

• When a charged object is brought close to an
  uncharged one the two objects attract each other.

8
Attraction and repulsion
TRIPLE ONLY

• Two bodies that carry different types of charge
  attract.
• Two bodies that carry the same type of charge
  repel.
• The law of charges
• LIKE CHARGES REPEL, UNLIKE ATTRACT.

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TRIPLE ONLY
10
TRIPLE ONLY
Choose appropriate words to fill in the gaps
below Static electricity occurs when electric
________ remains ____________ on an object. An
__________ object can be charged by __________ it
with another insulator. One of them gains
________ and becomes negatively charged. The
other becomes equally __________ charged. The law
of charges states that like charges _______,
unlike _________.
charge
stationary
insulating
rubbing
electrons
positively
repel
attract
WORD SELECTION
insulating
attract
repel
stationary
electrons
positively
charge
rubbing
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Hazards of static electricity
TRIPLE ONLY

• The main danger of static electricity is in
  situations where a spark can cause a fire or an
  explosion.
• The Buncefield oil depot explosion (opposite) in
  December 2005 was thought to have been caused by
  a spark.

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Fuel pipe problems
TRIPLE ONLY

• When oil or petrol is pumped along pipes a static
  charge can build up on the pipe which could
  result in a spark.
• This could cause an explosion when the fuel
  vapour reacts with oxygen in the air.

13
Antistatic floors
TRIPLE ONLY

• In operating theatres it is important that the
  doctors to do not become statically charged when
  walking around.
• This is because some of the anaesthetic gases
  used are explosive.
• Antistatic material is used for the floor surface
  so that any charge is conducted to earth.

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Uses of static electricity 1. Paint spraying
TRIPLE ONLY
The spray nozzle is connected is connected to the
positive terminal of an electrostatic
generator. As the paint droplets leave they repel
each other and spread out to form a fine cloud of
paint. The metal panel to be painted is connected
to the negative terminal. The negatively charged
metal panel attracts the positively charged paint.
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2. Ink-jet Printer
TRIPLE ONLY
Spots of ink are given an electric charge as they
leave the ink nozzle. The deflecting plates cause
the drops to hit the right part of the paper. The
charges on the deflecting plates change many
times per second so that each drop hits the paper
in a different position.
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3. Photocopier
TRIPLE ONLY
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TRIPLE ONLY
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4. Smoke precipitator
TRIPLE ONLY
An electrostatic precipitator is used to prevent
the dust and ash produced by coal fired power
stations from entering the atmosphere. The ash
and dust becomes charged as it passes through the
charged grid of wires. The ash and dust is then
attracted to the oppositely charged metal
plates. When the plates are shaken the
accumulated ash and dust falls down to be
collected and removed.
19
Online Simulations

• Balloons Static Electricity - PhET - Why does a
  balloon stick to your sweater? Rub a balloon on a
  sweater, then let go of the balloon and it flies
  over and sticks to the sweater. View the charges
  in the sweater, balloons, and the wall.
• Electric Magnetic Forces - 'Whys Guy' Video
  Clip (330mins) - Shows Charged Balloon Effect
  of a magnet on a TV screen.
• John Travoltage - PhET - Make sparks fly with
  John Travoltage. Wiggle Johnnie's foot and he
  picks up charges from the carpet. Bring his hand
  close to the door knob and get rid of the excess
  charge.

• Fuel Ignition While Refuelling A Car - Word
  document with embedded video clip
• Charged Rod Pith Ball - Iona
• Electric Force Tutorial - Science Trek
• How photocopying works - University of Delaware
• BBC KS3 Bitesize Revision
• Electrical Charge
• BBC AQA GCSE Bitesize Revision
• Attraction Repulsion
• Uses of static electricity
• Charge, current, energy and time relationships

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Electric ChargeNotes questions from pages 66 to
73
TRIPLE ONLY

1. Explain how a material can become charged using
   friction (see pages 66 67).
2. Describe a simple experiment to show that like
   charges repel and unlike charges attract (see
   page 67).
3. Explain with the aid of diagrams how the
   following devices make use of static electricity
   (a) paint sprayers (b) ink-jet printers (c)
   photocopiers (see pages 70 71).
4. Describe some of the problems caused by static
   electricity (see page 72).
5. Answer the questions on page 73.
6. Verify that you can do all of the items listed in
   the end of chapter checklist on page 73.

21
Online Simulations

• Balloons Static Electricity - PhET - Why does a
  balloon stick to your sweater? Rub a balloon on a
  sweater, then let go of the balloon and it flies
  over and sticks to the sweater. View the charges
  in the sweater, balloons, and the wall.
• Electric Magnetic Forces - 'Whys Guy' Video
  Clip (330mins) - Shows Charged Balloon Effect
  of a magnet on a TV screen.
• John Travoltage - PhET - Make sparks fly with
  John Travoltage. Wiggle Johnnie's foot and he
  picks up charges from the carpet. Bring his hand
  close to the door knob and get rid of the excess
  charge.
• Fuel Ignition While Refuelling A Car - Word
  document with embedded video clip
• Charged Rod Pith Ball - Iona
• Electric Force Tutorial - Science Trek
• How photocopying works - University of Delaware
• BBC KS3 Bitesize Revision
• Electrical Charge
• BBC AQA GCSE Bitesize Revision
• Attraction Repulsion
• Uses of static electricity
• Charge, current, energy and time relationships