protons for breakfast week 1: electricity november 2009
TRANSCRIPT
The plan for the evening…
7:00 p.m. to
7:59 p.m.
8:00 p.m.to
8:29 p.m.
Walkabout 8:59 p.m.to
9:00 p.m.
Feedback
Talk
8:30 p.m.to
8:59 p.m.
More talk
Who is helping? • Jonathan Pearce• Laurie Winkless• Lindsay Chapman• Mateusz Szymanski• Matthew Tedaldi• Clive Scoggins• Neelaksh Sadhoo• Paul Carroll• Peter Quested• Peter Woolliams• Piers de Lavison• Rainer Winkler• Richard Gilham• Robin Underwood• Ruth Montgomery• Sharmila Hanson• Stephanie Bell• Tim Burnitt
• Amanda Law• Andrew Hanson• Arzu Arinc• Averil Horton• Bufa Zhang• Deborah Lea• Emma Woolliams• Gianluca Memoli• Heather Browning• Jacquie Elkin• James Miall• Jeff Flowers• Jenny Wilkinson• Jian Wang• Joanna Lee• John Makepeace• John Mountford
Acknowledgements
• NPL:– The National Physical Laboratory
• Serco:– Manage NPL on behalf of the BIS
• Amey:– Who set out the rooms
• Baxter Storey:– Who do the tea & biscuits
Who is Michael de Podesta?
Age 49:• Lecturer in Physics at
Birkbeck College and University College London for 13 years
• Scientist at NPL for 9 years.
• Building the most accurate thermometer ever.
• Married with two sons (aged 11 & 13)
• Keen on Water Rockets• MBE!
Why are you here?
A selection of your reasons for attending…• My son and I are very interested in learning about science• To improve my understanding and my teaching of Physics.• I am interested in all aspects of science and how it affects
us and everything around us.• To try to understand more about the world (more than I can
take in from reading).. • I love Physics! I am very interested in Physics as a potential
career.• It looks very interesting and I want to share the experience
with my daughter who will then be in Year 8.• Poor Science lessons at my grammar school. Teachers
seemed more concerned with neat writing• Near total ignorance. No Physics since 1944
Why am I here?
I am here because I believe …
Science is humanity’s greatest achievement
But there is a problem about how we, as citizens, relate to science…
The image of science:1Mad Muppets top cult science poll
Dr Honeydew is known the world over for his disastrous research at Muppet Labs,
"where the future is being made today".
His experiments invariably go awry, with poor old Beaker usually being blown to bits or electrocuted. BBC 6/9/2004
In contrast…
• A room full of people who want to learn about science• Helped by volunteers • In a world where ignorance makes us powerless
Tonight’s talk
• The scale and size of the Universe – Its very big, but full of very small things
• The electric force– It dominates every physical phenomenon on our scale.
• How the force works– Electric particles– Electric field
• Light– Waves in the Electric field
The imperceptible and the vast (1)
As human beings we can judge:• temperatures close to ‘normal’
• weights greater than a gram up to around 1000 kilograms
• distances greater than a millimetre or less than a few kilometres.
• times greater than a second or less than a fraction of a lifetime.
The imperceptible and the vast (2)
As human beings we cannot judge:• temperatures more a few degrees away from ‘normal’
• Such temperatures just feel ‘very hot’ or ‘very cold’• weights beyond a few tonnes or less than a gram
• Such weights seem either stupendously heavy or negligible• distances less than a millimetre or greater than a few kilometres.
• Such distances are too tiny or too far to perceive directly• times less than a second or more than a fraction of a lifetime.
• Such times are too small or too long for us to appreciate
The imperceptible and the vast (3)
Quantities and qualities that extend beyond our ability to perceive them often seem:
imperceptible or vast
? ?
The imperceptible and the vast (4)
• Measurement: Quantitative comparison• Measuring instruments extend our senses
• Telescopes & Microscopes, • Weighing machines,• Devices sensitive to electricity & light, • Clocks
• NPL• Enables people to trust measurements
The imperceptible and the vast (5)
• We can be unaware of things because they are– Too small– Too large– Change too quickly– Change too slowly
• Science can help us to quantitatively assess matters we commonly perceive as imperceptible or vast
– But these things can still induce a feeling of being ‘boggled’
Powers of Ten
I hope that you are now a little unsettled and ready to go on a 9 minute journey to see how the world looks at different levels of ‘fantasy magnification’
Photo Credit: Powers of 10
Very Very Small
Very Very
Large
Powers of Ten (1)
1 metre
1000 m
1000000 m
1000000000 m
1000000000000 m
0.001 m
0.000001 m
0.000000001 m
Can you see the problem with very small and very large numbers?
Powers of Ten (2)
Very Very Small
Very Very
Large
1
1000103
106
109
1012
1015
1000000
0.00110-3
10-60.000001 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12
100
Powers of Ten (3)
Very Very Small
Very Very
Large
1 metre
103
106
109
1012
101510-3
10-6 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12 1012
1000000000000 m
0.000000000001 m
Powers of Ten Length Scale in metres
Very Very
Large103
106
109
1012
101510-3
10-6 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12
?Very Very Small
100
Human Relationships
Atoms & molecules
Nucleiof atoms
Current estimate of the size of the
universe
Nearest StarLight YearTallest MountainNanotechnology
Distance to the Sun
Diameter of the Earth
Diameter of a hair
MicrobesViruses
Quarks
Powers of Ten Length Scale in metres
103
106
109
1012
101510-3
10-6 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12 100
Human Relationships
Distance to the Sun
Atoms & molecules
Nucleiof atoms
Current estimate of the size of the
universe
Nearest StarLight YearTallest MountainNanotechnology
Diameter of the Earth
Diameter of a hair
MicrobesViruses
Quarks
Powers of Ten Global Warming
Very Very
Large
100
103
106
109
1012
101510-3
10-6 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12
Very Very Small
Human Relationships
The phenomenon of global warming involves physical processes with
length scales spanning 20 powers of 10!
Distance to the Sun
Tallest Mountain
Diameter of the Earth
Atoms & molecules
Microbes
Powers of Ten Nuclear Power
Very Very
Large
100
103
106
109
1012
101510-3
10-6 1018 1024 1030 1036
1021 1027 103310-15 10-9
10-18 10-12
Very Very Small
Human Relationships
Tallest Mountain
The issues surrounding nuclear power involve
physical processes with length scales spanning 25
powers of 10!
Nucleiof atoms
Distance to the Sun
Diameter of the Earth
Atoms & molecules
Microbes
Powers of Ten (time)Time scale in seconds
Very Very short
Very Very Long
100
103
106
109
1012
101510-3
10-6 1018 1024
102110-15 10-9
10-18 10-12
Time for a molecule to jiggle once
Light wave wiggles once
Earthmoves once
around the Sun
Estimated time since the big bang
Age of the EarthEnd of last ice age
Lifetime of a Civilisation
A human lifetime
Fastest response of human
eyeSound
travels 1 metre
1 second
…its everything…
The balloon affects anything and everything nearby
To understand this, we need to understand • what matter is made of, and • how this ‘influence’ is communicated across ‘space’
A simple scientific instrument: The gold leaf electroscope
• Scientists can develop instruments to measure the relative strengths of the ‘electric influence’
• Based on the same effect we saw with bits of paper
The Van de Graaff Generator
• Scientists can develop machines to automate and amplify the ‘rubbing’ process with the balloon
Photo Credits: Katherine Robinson and MIT
The Van de Graaff Generator
It is not important to understand how a Van de Graaff generator works
PictureCredits: http://www.ikp.uni-koeln.de/~3T/tandem-prinzip1.htmlhttp://science.howstuffworks.com/vdg1.htm
The Wimshurst Machine
Sorry: I cannot easily explain how a Wimshurst Machine works!
Photo Credits: Wikipedia and http://www.coe.ufrj.br/~acmq/electrostatic.html
Electrostatic Generators
• People have been doing this for a long time…
Photo Credits: http://www.ikp.uni-koeln.de/~3T/tandem-prinzip1.html
Conclusion…
Electricity is present inside ALL matter
Its ‘influence’ can be communicated
across ‘empty’ space
How do we describe the world?
Not Stuff (Fields)• Fields
• Gravitational• Electroweak• Strong
• Extend throughout space
Stuff (Particles)• Atoms
• Electrons• Neutrons• Protons
• Very small
We need to know about both particles and fields
Two different kinds of physical entity
The electrical nature of matter
Particle
with electric charge
Particle
with electric charge
Interact by meansof an electric field
Tonight’s talk…(3)
• The scale and size of the Universe – Its very big, but full of very small things
• The electric force– It affects everything
• How the force works– Electric particles– Electric field
• Light– Waves in the Electric field
The electrical nature of matter
• Electric charge is a fundamental property of electrons and protons.
• Two types of charge (+ and -)• If particles have the same sign of electric charge they repel• If particles have different signs of electric charge they attract• The forces (attractive or repulsive) get weaker as the particles get
further apart.
The electrical nature of matter
• Electric charge is a fundamental property of electrons and protons.
• Two types of charge (+ and -)• If particles have the same sign of electric charge they repel• If particles have different signs of electric charge they attract• The forces (attractive or repulsive) get weaker as the particles get
further apart.
Atoms are small• Think of a millimetre
Atoms
1 mm
0.1 mm0.01 mm0.001 mm
• Atoms are roughly 10,000 times smaller than this…
Atoms
• There are VAST numbers of atoms in everything.– In just a handful of anything there are about the
same number of atoms as there are grains of sand on all the beaches and deserts on Earth combined
Photo Credit: http://www.morguefile.com ID = 104101
How are atoms made?
proton
Interact by the short range ‘strong’ force – not electrical
Electrical Repulsion
Atoms (4)
Electrons• ‘orbit’ around the outside of an atom• very light• possess a property called electric charge
Nucleus• occupies the centre• very tiny and very heavy• protons have a property called electric charge• neutrons have no electric charge
How are atoms made?
• Nuclei (+) attract electrons (-) until the atom as a whole is neutral• The electrons repel each other
– They try to get as far away from each other as they can, a– and as near to the nucleus as they can
AtomsThe Periodic Table
• Atoms with up to about 82 protons can be stable.• A material made up of a single type of atom is called an element
H
Atoms& Molecules
H2
N
N
• A molecule is a collection of atoms stuck together electrically.
H
H
0
H20
H
N2
The electrical nature of matter
• In ‘normal’ matter, there are equal quantities of positive and negative charge so that there is no attraction or repulsion of objects.
Object 1
Object 2
Atoms and mechanics(9)
• Whenever two materials touch, the forces between them are the forces between the outer (valence) electrons
• All mechanical forces are actually electrical in nature
Object 1
Object 2
Atoms in solids (8)
Solids are made up out of lots atoms very close together.
– If the electrons can’t move easily from atom to atom: • The material is called an insulator
– If the electrons can move easily from atom to atom: • The material is called a conductor
The electrical nature of matter
How is the electrical force transmitted from one charged
particle to another?
How do charged particles interact?
It’s a three-step process…
Particle
with electric charge
Particle
with electric charge
Interact by meansof an electric field
…but the steps happen very quickly
Tonight’s talk…(4)
• The scale and size of the Universe – Its very big, but full of very small things
• The electric force– It affects everything.
• How the force works– Electric particles– Electric field
• Light– Waves in the Electric field
Summary
• Physics concepts span vast ranges of mass, length and time.
• The universe has two kinds of objects in it: Matter and Fields
• All matter (on Earth) is made of atoms which interact electrically.
• In matter as we normally experience it, there are equal amounts of the two types of electric charge and their effects cancel
• If we add or remove some particles with electric charge from matter then we can see the electrical effects.
Homework
• Activity: Remember when you have your breakfast that you are eating protons and neutrons coated with tasty electrons.
• Research: What is the ‘frequency’ of your favourite radio station? Don’t just get the number (98.9, 198 etc.) get the units as well! They should be in – Hertz– Kilohertz– Megahertz
One minute feedback
• On the back of your handouts!• Rip off the last sheet• Please write down what is in on your mind RIGHT NOW!
– A question? OK– A comment? OK– A surprising thought in your mind? I’d love to hear it!
On-line Resources
• www.protonsforbreakfast.org –This PowerPoint ™ presentation.–Handouts as a pdf file
• blog.protonsforbreakfast.org –Me going on about things
• links.protonsforbreakfast.org –Links to other sites & resources