Magnetism
Activity Booklet
Ivanhoe Girls’ Grammar School
Introduction
A magnet is an object made of certain materials that creates a magnetic field, like the one shown in
the above diagram of the Earth. Every magnet has at least one North Pole and one South Pole. By
convention, we say that the magnetic field lines leave the North end of a magnet and enter the South
end of a magnet.
The ancient Greeks and Chinese discovered that certain rare stones, called lodestones, were
naturally magnetized. These stones could attract small pieces of iron in a magical way, and were
found to always point in the same direction when allowed to swing freely suspended by a piece of
string. The name comes from Magnesia, a district in Thessaly, Greece.
For many years magnetism was just a curious natural phenomenon and its only use was in
navigation, using what we now refer to as the mariner's compass. It was probably first developed by
the Chinese some 4500 years ago. The earliest mariner's compass comprised a splinter of loadstone
carefully floated on the surface tension of water. Until the invention of the magnetic compass
proper, travellers used to carry small portable lodestones that they suspended freely in order to
locate north.
In this booklet you will find a number of experiments that will help you to learn more about
magnets and magnetism.
If you would like to find out more about magnets the following websites will help you.
http://www.le.ac.uk/se/centres/sci/selfstudy/mam.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html
EXPERIMENT M1 - MAGNETIC FIELDS
What is a magnetic field? What do magnetic fields look like?
All magnets produce a magnetic field at all points in the space around it. It can be defined by
measuring the force the field exerts on a moving charged particle, such as an electron. Magnetic
field lines are a way to visualize the magnetic field. When drawn, the distance between them is an
indication of the strength of the field. The closer they are, the stronger the field.
If you look at the iron filings floating in oil you will see that they have lined themselves up with the
magnets’ magnetic field. In the box provided draw the magnetic field lines around the magnet.
N
S
For each of the following situations arrange the magnets as shown in the accompanying
diagrams.
Place a piece of Perspex or OHP transparency over the top of the magnets and then gently
sprinkle iron filings onto the transparency to determine the shape of the magnetic field
around the magnets.
In the box provided draw the magnetic field lines around, and between, each of the magnets when
they are arranged as shown.
S
N
S
N
In the box provided draw the magnetic field lines around, and between, each of the magnets when
they are arranged as shown.
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N
N
S
In the box provided draw the magnetic field lines around, and between, each of the magnets when
they are arranged as shown.
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N
S
N
In the box provided draw the magnetic field lines around, and between, each of the magnets when
they are arranged as shown.
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In the box provided draw the magnetic field lines around, and between the arms, of the horseshoe
magnet.
EXPERIMENT M2 - MAGNETIC FORCE
What happens when two magnets are brought close together? Are they attracted to each
other, or do they repel each other?
Try bringing the North Poles of two magnets close together. What happened?
S
N
N
S
Try bringing the Opposite Poles of two magnets close together. What happened?
S
N
S
N
Use your newfound understanding of magnets and magnetic fields to try and explain how the
‘Levitron’ toy shown in the diagram below works. Include a labeled diagram as part of your answer.
EXPERIMENT M3 - MAGNETIC OBJECTS 1
What sorts of objects are attracted to magnets?
Use the magnet provided to test each of the following objects to see if they are attracted to the
magnet. Place a tick in the box if it was attracted to the magnet, and a cross if it wasn’t.
Glass
Wood
Steel
Rubber
Nickel
Silicon
Carbon
What types of objects seem to be magnetic?
EXPERIMENT M4 - MAGNETIC OBJECTS 2
What sorts of metals are attracted to magnets?
Use the magnet provided to test each of the following metals to see if they are attracted to the
magnet. Place a tick in the box if it was attracted to the magnet, and a cross if it wasn’t.
Aluminium (Al)
Zinc (Zn)
Iron (Fe)
Copper (Cu)
Nickel (Ni)
Tin (Sn)
What types of objects seem to be magnetic?
EXPERIMENT M5 – MAGNETISM & ELECTRICITY 1
Is there a connection between magnetism and electricity?
What happens to the compass needle when the power supply is switched on and current flows
through the coil?
What does this suggest about the connection between electricity and magnetism?
EXPERIMENT M6 – MAGNETISM & ELECTRICITY 2
If electricity can create a magnetic field, can a changing magnetic field create electricity?
When you place the magnet inside the coil of wire (solenoid), what happened to the needle on the
galvanometer? A galvanometer is device that can detect the flow of small amounts of charge
(electricity).
What happened to the needle on the ammeter when you stopped moving the magnet?
What happened to the needle on the ammeter when you withdrew the magnet from the solenoid?
What happens to the needle on the ammeter when you quickly move the magnet in and out of the
solenoid?
What connection can you make between electricity and magnetism?
EXPERIMENT M7 – ELECTROMAGNETS
Can we use electricity and a magnetic material to make a stronger magnet?
Use the iron rod to try and pick up some of the paper clips. Did you succeed?
Switch on the power and see if the solenoid can pick up any paper clips.
Now place the iron rod inside the solenoid, switch on the power and try again to pick up the paper
clips. Did it work this time?
EXPERIMENT M8 – D.C. MOTORS
Can we use a current carrying wire and a magnetic field to make a machine that does useful
work?
Press the switch down to complete the circuit and describe what happens to the coils of wire. You
may need to gently nudge the coils to get them started.
Can you explain how the motor works?
Additional notes for teachers.
A magnetic field is defined to be a region of space near a magnet, electric current, or moving
charged particle in which a magnetic force acts on any other magnet, electric current, or moving
charged particle.
Experiment M1
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Experiment M2
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S
S
Magnetic levitation toys
Experiment M5
Oersted's Law.
http://www.hsphys.com/electromagnetism.html
To see the effect observed and recorded by Oersted the compass needle is placed parallel with the
wire before the switch is closed. When closed the current in the wire creates its own magnetic field,
which will interact with the magnetic field around the compass needle causing the needle to rotate
as shown in the second diagram.
Experiment M6
Electromagnetic Induction.
For a more detailed explanation of the
principles of magnetic induction consult
with your school's physics teacher or a
year twelve physics text.
In simplest terms when the strength of a
magnetic field changes it will induce
(cause) a current to flow in a solenoid (coil
of wire). The magnetic field associated
with the current in the solenoid will
oppose the changing magnetic field that is
causing the induced current.
Experiment M7
Electromagnet.
Experiment M8
D.C. Motor
There is a great series of animated videos that were made in 1987 by TVOntario called 'Concepts In
Science'
The six episodes are titled:
1. Earth's Magnetic Field
2. Magnetism And Electron Flow
3. Domain Theory
4. The Motor Principle
5. Electromagnetic Induction
6. Life In The Field
http://www.youtube.com/watch?v=bht9AJ1eNYc
The Invisible Beaker
Place a 150 mL Pyrex beaker, preferably
without any writing on it, inside and in the
middle of an empty 500 mL beaker.
Now pour some canola vegetable oil into the
smaller beaker until it overflows and
eventually is surrounded inside and out by the
canola oil.
What do you ‘see’ happening to the 150 mL beaker as the oil overflows into the larger beaker?
Use your understanding of refraction, reflection and how it is that we actually get to see things to
explain what you have just seen.
Answer
In order for us to see an object, light from the object has to reach our eyes. There are two ways in
which this can happen. The first is that the observed object is luminous and the light we see comes
directly from it. The second occurs as a result of scattering (reflection) whereby light from a source
is reflected from off the object to our eyes.
When light is incident at a boundary between two materials of different refractive indices (optical
density) as well as refraction occurring, some of the light is reflected. Hopefully you and your
students will have noticed this when you did the refraction experiment on pages 80 and 81 of
Science Links 3. An example of this partial reflection from the boundary between two surfaces is
shown in the diagram below. Remember that the angle the reflected ray makes with the normal will
be equal to the angle of incidence.
So how does the demonstration work?
Well, in this particular instance the Pyrex glass and the Canola oil both have the same index of
refraction; therefore there is no light reflected (scattered) from the glass-oil boundary and the 150
mL beaker magically disappears!
Reflection Illusions - The Cold Candle
PIRA 6A10.60
http://www.physics.isu.edu/physdemos/optics/reflect1.html
Place two identical candles on opposite sides, and equidistant from, a vertical pane of clear glass as
shown at right. Adjust their positions so that each lies at the image point of the other for reflections
from off of the glass. If only one candle is lit, it appears as if the other one is lit as well, if the
observer is on the same side of the glass as the lit candle. This works best on a wheeled cart that can
be turned to show the view from different angles and from the other side.
An amusing variation is to have one of the candles inside a beaker, but still at the image point of the
other candle. With the other candle lit, the beaker can be filled with water to make it look as if the
candle is burning underwater.
This is the basic idea behind a whole series of vaudeville stage illusions, such as the "head in the
box" and the "ghost king on the throne" tricks. The Haunted House at Disneyland uses this quite a
bit too. David Copperfield used this to make the Statue of Liberty "disappear".
And the magic candle that burns under water…
YouTube Video Clip
http://www.youtube.com/watch?v=YqbRiz9Ky50
Explanation:
http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/peppers-ghost/
Although glass is mostly transparent, it
reflects a significant proportion of the light
that hits it. Normally the light going
straight through is so much brighter that
you can't see it, but if you use something
bright, like a candle, in front of the glass
and a dim room behind, the reflection can
dominate what you are seeing.
So you see the reflection really well. The
neat thing about reflections is that they
look as if the object is behind the mirror.
So when you move your head, the
reflection moves in exactly the same way
as the candle behind, so the illusion works
from lots of directions.
The demonstration clearly shows that an image formed in a plane mirror is:
• Virtual
• Upright
• Same size as the object
and
• Laterally inverted (look carefully at the candle flame and its image when it flickers)
Figuring Physics – Hewitt Drewit!
The Physics Teacher – Vol. 37, Feb. 1999
Question
The lens projects an image of a white candle on a screen. How would the image differ if the top half
of the lens is covered with a green filter and the bottom half with a red filter?
green filter
object
image
red filter
convex lens
Answer
The image of the candle will be yellow. Each and every part of the image on the wall is formed
from light that passes through each and every part of the lens. The red and green light transmitted
by the lens will simply overlap and average to be yellow.
Additional Questions
Write down your predictions to each of the following questions,
trial them experimentally and comment on your findings.
1. How would the image differ if the top half of the lens is
covered with a red filter and the bottom half with a blue filter?
green
red
blue
2. How would the image differ if the lens was 1/3 covered with a
red filter, 1/3 covered with a blue filter and 1/3 covered with a
blue filter as shown in the diagram to the right?
3. How would the image differ if the bottom half of the lens was
covered by an opaque card?
Answers
1. The image of the candle will be magenta. Each and every part of the image on the wall is formed
from light that passes through each and every part of the lens. The red and blue light transmitted
by the lens will simply overlap and average to be magenta.
2. The image of the candle will be white. Each and every part of the image on the wall is formed
from light that passes through each and every part of the lens. The red, blue and green light
transmitted by the lens will simply overlap and average to be white.
3. The image of the candle will be white, but dimmer. Each and every part of the image on the wall
is formed from light that leaves each and every part of the candle and passes through the
uncovered half of the lens. See the accompanying ray diagram.
opaque filter
object
image
f
•
f
•
convex lens
Modelling electric current
using your students and
M&Ms.
This is my slightly modified version of one of Christina Hart's models for electric circuits that she
presented at the Physics Teacher's Conference a few years ago. Her original articles can be found on
the VICPhysics website via the url below.
Model 4: Energy in a simple circuit:
The ‘smarties’ model
By Christina Hart (STAV Physics Teacher's Conference 2008)
http://www.vicphysics.org/electricity.html
Instead of each student representing a single electron I have each student represent one coulomb of
charge, and that the atoms of their body represent the number of electrons that are required to make
up one coulomb of charge.
Remember to have your students move from the negative terminal of your battery to the positive
terminal.
The charge on a single electron is 1.60 x10-19 C.
It takes 6.25 x1018 electrons to make up one coulomb of charge.
→
−19
÷1.6×10
coulombs×1.6×10
−19 electrons
←
The M&Ms are still use to represent energy, the energy that each coulomb of charge has. It is also
important to impress upon the students that energy is not a thing – even though we are representing
it with sugar coated chocolate!
Using this modified model I can talk about:
Current.
Current (A) = charge (q) / time (s)
The number of students that walk past a point in the circuit each second is equal to the current flow
in the circuit.
Energy
Energy (J) = voltage (V) x charge (q)
The number of M&Ms given to each student represents the energy in joules given to each coulomb
of charge that flows out of the battery. This energy has to be 'given up' to the various loads within
the circuit so that each coulomb of charge returns to the battery with 0J of energy.
Colour Addition
A useful set up uses 3 overhead
projectors. I cut out some circles in
manilla folders and stuck on
coloured cellophane. Two layers for
blue and red, 3 for yellow.
This gives surprisingly good results,
the centre is close to white.
I usually show an app that labels
the colours.
Subtraction of colour
Use quality filters PFG
With secondary filter (eg magenta that
lets through red and blue) on overhead,
overlap with another secondary (eg
yellow, that lets through red and green,
therefore the overlapped section will be
red)
magenta
blue
(s)
(p)
red
(p)
yellow
(s)
Light Spectrum
Turn on camera on computer (webcam, iPad etc) on point a remote
control at it. Pressing buttons will flash codes on the IR LED. This
part of the spectrum is “seen” by a CCD camera.
Human view versus insect/predator view.
Polarising – insects (eyes – IR and UV) CCD camera spectrum
Polarising lens demo. Sticky tape of microscope slide.
http://www.youtube.com/watch?v=E9qpbt0v5Hw
(Polarization of Light uclaphysicsvideo)
cyan
(s)
green
(p)
white
Detecting radiation with a Geiger-Müller tube demonstration (based on Heinemann exp)
TASK
To investigate the penetrating ability of three common types of nuclear radiation and the ability
of different materials to absorb the energy associated with nuclear radiation.
THEORY
Besides the obvious fact that none of our senses can
detect individual decay events, the nuclear decay
process seems to be random, yet, at the same time,
predictable. It is impossible to say which nucleus will
become unstable enough to decay next, but it is fairly
easy to use a Geiger counter to count the number of
nuclei which decay per second throughout a radioactive
sample.
DATA & ANALYSIS
Part I: Background radiation
Count 1:
Count 2:
Count 3:
Count 4:
Average count during activity:
……….
……….
……….
……….
……….
1. How do these values demonstrate the random nature of radiation.
Part II: Radiation shielding - Source Am241
Record your final data as the net count per 60 seconds (i.e. the recorded count minus the
average background count).
Alpha Source
Material
Beta Source
Count
Material
Gamma Source
Count
Material
Air
Air
Air
Paper
Paper
Paper
Glass
Glass
Glass
Aluminium
Aluminium
Aluminium
Lead
Lead
Lead
Count
QUESTIONS
1. Which type of radiation is the most penetrating?
2. Which type of radiation is the least penetrating?
3. What generalisation can you make about the effect of the thickness of the shielding material
on the count rate?
4. What generalisation can you make about the effect of the density of the shielding material on
the count rate?
5. Why was background radiation measured? Do you expect the value to be constant?
Demo: Measuring Radioactivity
Demonstration 1: Ionising radiation from different sources
Source
Geiger count / 10sec
(at 20cm)
Geiger count / min
(at 20cm)
Background
Uranium ore
Mobile phone
Americium-241 (alpha emitter)
Strontium-90 (beta emitter)
Cobalt-60 (gamma emitter)
Demonstration 2: Materials that block ionising radiation
Source
Americium-241
(alpha emitter)
Strontium-90
(beta emitter)
Cobalt-60
(gamma emitter)
Material
Count @20cm
/min without
material
Count @20cm
/10sec with
material block
Count @20cm
/min with
material block
Paper
Glass
Aluminium
Lead 2mm
Lead 10mm
Paper
Glass
Aluminium
Lead 2mm
Lead 10mm
Paper
Glass
Aluminium
Lead 2mm
Lead 10mm
1. Identify which material is needed to effectively reduce each type of radiation
nearest to background levels:
Alpha:
Beta:
Gamma: