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DEMOSTRATION AND TECHNOLOGY IN SCIENCE EDUCATION
Magnetism
The world according to Jon, Gregory and Max
By Max Borghard
2009
Magnetism
Contents
Chapter 1 History............................................................................................................................. 3
Chapter 2 Lesson Description .......................................................................................................... 5
Chapter 3 Teacher’s Lesson Plan ..................................................................................................... 7
Chapter 4 Biographies ................................................................................................................... 20
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Magnetism
Chapter 1 History
1) Discovery of Lodestones
a) Discovered by Greek herdsmen as early as 600 BC
i)
Observed that iron objects became “stuck” to some stones where their sheep grazed
b) Thales of Miletus hypothesized that the attraction to iron was due to the lodestone
containing a soul or spirit
i)
Lodestones could interact at a distance
ii) Could exert a force through different materials (through cloth/parchment)
c) Lodestones were mined in a section of Greece that had a high concentration of the stones.
i)
Area was named Magnesia
ii) Lodestones became synonymous with Magnets
2) First applications using lodestones
a) Chinese first used lodestones as a “south pointer” around 400 BC
i)
Carved a ladle out of lodestone which could rotate on a flat board
ii) Used for divinity purposes and later adapted to navigation
b) Later used as a method of navigation for travelers
3) Recognizing magnets and characteristics
a) William Gilbert’s On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth
(1600)
i)
Performed experiments with his model “terella”
(1) Concluded that the Earth is one giant magnet, not a magnetic island at the north pole or
the north star
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Magnetism
(2) Argued that the center of the Earth was largely made of iron
(3) Showed that when magnets are cut they form new smaller magnets with poles.
4) Electricity and Magnetism
a) Alessandro Volta (1745-1827)
i)
Developed the “Pile” in late 1799
(1) Originally was pursued to replicate the electrical potential seen across Leyden Jars
(2) Development of the pile allowed widespread access to source of relatively constant
electrical potential
b) Hans Christian Ørsted (1777-1851)
i)
Accidental observation while setting up experimental equipment
(1) Magnetic north of nearby compass was deflected when the terminals of a battery (Volta’s
pile) were connected
(2) Believed that magnetic influence extended itself from a current carrying wire similar to
magnets
ii) Was unable to provide a comprehensive explanation of the phenomenon.
c) François Jean Dominique Arago (1786-1853)
i) Observational experiment with iron filings around a wire showed that similar to magnets,
a current carrying wire could remotely interact
d) André-Marie Ampère (1775-1836)
i)
Took and built upon the initial findings of Ørsted
(1) Wrote: Memoir on the Mathematical Theory of Electrodynamic Phenomena (1826)
(2) Was able to provide an explanation of electromagnetic phenomenon unlike Ørsted
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Magnetism
Chapter 2 Lesson Description
This particular lesson focuses on the ISLE cycle of the students building a baseline of
observations from experiments and previous in-life experiences to help them to develop the
concepts of magnetism and electricity.
The initial story and description sets the discovery of lodestones which set the way for the
modern term magnets as being derived from the area where lodestones were mined in
Magnesia. The students should also know that here lodestones found their initial use as a
compass, where travelers would take a shard of lodestone and hang or float it in water. Also
there should be mention that it was because of the work later on by William Gilbert did they
believe that the earth was a gigantic magnet which exerted an influence on the smaller
magnetic lodestones.
With the first experiment they simply observe the interactions between two magnets. Here
they begin to understand that magnets can interact at a distance and has two differing poles.
Be sure that the students realize that the strength of the interaction changes with distance as
this is important later on when deriving the force felt by a current carrying wire in a magnetic
field. Also, ask them what kind of earlier forces this is similar to (gravity, electrostatic attraction,
etc.), but be very specific to point out how they are also different. For instance the magnetic
interaction much like the electrostatic force and gravity interacts in a distance without direct
contact. However, unlike gravity, the magnetic force is very strong like the electrostatic force
comparatively (a magnet can lift a paper clip), and we KNOW that this is not the same force
from earlier lessons. So in effect you let the students find out that they are studying an entirely
different phenomenon than what was observed and explored by them before.
The second experiment is another observational experiment which builds upon the things
learned from the first experiment. Since the students can qualitatively describe the interaction,
now we can place a quantitative number of the interaction. Here, the important thing from this
experiment is to see that the force is inversely related to the distance. There is no current need
to create a force vs. distance formula at the moment, however use of excel or another plotting
tool can easily show how it is non-linear in nature.
Now, the third experiment sets up the idea that there is more to magnets than simply a remote
interaction, that there is a defined direction of whatever is doing this remote interaction. We
should be careful not to use the concept of a field yet here unless it was specifically stated
earlier, as it was only after these experiments later on by Faraday that the field concept was
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Magnetism
introduced. When the students draw the directions of the compass they can begin to see how
the field is shaped, as the compass’ magnetic north always pointing away from the north pole of
the magnet and towards the south pole. As an important note, be very careful as to what the
magnetic north on your compasses are. Some have dual colors and can easily confuse the
student. During this time you can also sprinkle iron filings above a covered bar magnet to show
these lines of interaction. Students should see that these lines do not stop once they reach the
edge of the magnet but extend THROUGH the magnet in a closed loop. The students should
understand that the compass can show the direction of interaction and if any magnetic
interaction exists at all.
Now we move on to do a reenactment of Orsted’s observation when he was setting up
for different experiment for his friends. With a compass near a wire, current is allowed to flow
through the wire showing a deflection in the direction of the compass. It is good to show the
students how a simple historical observation lead to flood of advancements with magnetism and
electricity. To build on Orsted’s observation, the next experiment is a loop of wires with current
running in the same direction in all the wires. The compasses are placed below the wires with
the initial direction on the compasses pointing parallel with the wires. As the current is turned
on, the students will observe the compasses turning perpendicular to the wires and when the
current is reversed, the students will observe the direction of the compasses reversing direction.
The goal is for the students to hypothesize that the magnetic field has a direction (a right hand
rule) associated with the direction of the current flow. The students are then asked to come up
with a testing experiment using the magnetic field of the current carrying wire. Hopefully they
will come up with a magnet interacting with a wire with current flow. They will be shown a video
of a wire jumping out of a horseshoe magnet when the current is turned on. Here we help the
students to develop a hypothesis of the relationship between the direction of magnetic field,
the current direction and the force of the magnetic field which is another right hand rule.
We talk to the students now about two parallel wires and how they might interact with
current flowing through the wires. The students should be able to predict that the wires will
interact with each other because of the magnetic field. As they observe the two wires attract
each other, the students will be able to see the relationship again of the right hand rule. The
students should be able to come up with a hypothesis about the interaction of the two wires
with opposite current directions. The students should be able to come up with the prediction
that the two wires will repel each other when the current in one of the wires had been reversed.
In the last exercise, the students are given data that has been massaged to work with in
order to come up with a mathematical relationship between force, the magnetic field, the
current and the length of wire. The student should be able to come up with the formula that
shows F=IBL.
6
Magnetism
Chapter 3 Teacher’s Lesson Plan
Magnetism Lesson
Class 9
Introduction
Today we will be exploring and developing the concept of magnetism. Magnetism is one of the
fundamental forces
Fundamental Forces
Observations of magnetic interaction have been around for thousands of years through the
existence and use of natural magnets. The earliest known discoveries of natural magnets were
lodestones as early as 600 BC by both the Greeks and the Chinese. These lodestones were often
considered magical or spiritual in nature due to their magnetic properties.
Importance of magnetism for modern life cannot be overestimated. Just look around and you
will see computer hard drives, speakers, el.motors, cell phones (radio), a galvanometer and
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Magnetism
cyclotron and millions more devises. And don’t forget that we are able to live only because
magnetic field protects us from deadly cosmic radiation. So, to survive we need to know
surrounding were we live.
Observe the interaction between two bar magnets.
Qualitatively describe the interaction between the magnets.
Does this type of interaction require physical contact between the magnets? Is this similar to
any other type of interaction you are already familiar with?
N
S
N
S
I think we should hold off with the iron filings and go to step 2 because we will have hinted
towards the similarity between gravitational pull and magnets as they relate to the distance
between the two objects and the strength of the force. So let’s go to step 2 first.
Faraday proposed that electromagnetic forces extended into the empty space around the
conductor. This idea was rejected by his fellow scientists, and Faraday did not live to see this idea
eventually accepted. Faraday's concept of lines of flux emanating from charged bodies and
magnets provided a way to visualize electric and magnetic fields. That mental model was crucial
to the successful development of electromechanical devices which dominated engineering and
industry for the remainder of the 19th century.
Here I believe we should make a statement about Faraday’s magnetic field concept although it
came after this, historically. This way we can clear the use of “magnetic field”. We should
definitely tell them not to use the term for granted but actually question WHAT the magnetic
field concept is? HOW do we describe the field? I’m thinking the iron filing experiment would go
best here as they can now actually see the field.
Perform an observation experiment.
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Magnetism
How does the force that one magnet exert on the other change with distance?
What is a best approximation of F1on2 versus d?
Start with 24 playing cards and put them between the two magnets with the hooks trying to
center the magnets on the playing cards. Hang the magnets with the cards on the horizontal bar
and start adding weights to the bottom magnet hook until the magnets separate. Weigh the
total amount of weight.
Repeat the process with 18, 12, 6 and 0. NOTE: We need to make sure we have enough weight
for 0 cards – about 13 pounds for two stations
Make a graph of the data of F1on2 versus d
D (cards)
Mass (g)
F1on2(N)
15
473
4.6354
33
89.5
0.8771
12
715
7.007
30
146.5
1.4357
9
906
8.8788
27
174.7
1.71206
6
1255
12.299
24
203.3
1.99234
3
1843
18.0614
21
273.8
2.68324
0
3009
29.4882
18
381
3.7338
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Magnetism
Force vs distance
35
30
Force (N)
25
20
15
10
5
0
-5
5
15
25
35
# of Cards
10
Magnetism
D
(cards)
Mass
(g)
F1on2(N)
24
18
12
6
0
Here we can use this observation experiment to show the students a very important point that the
magnetic field strength varies with distance. This will be important later on to understand how we can
change the strength of the magnetic field without actually knowing its exact value for step 9. . Max,
here is a good part to put your stories on compasses. Make sure the stories emphasize that compass is a
tool that can indicate the existence of a magnetic field.
Magnetism is a phenomenon that is quite similar to another interaction of bodies that we have studied
earlier in the semester. What is interesting about magnetism though is that it is much stronger than the
previous phenomenon but has similar characteristics.
These earliest known magnets called lodestones and they are a type of iron ore (FE3-O4) called
magnetite. Even though all varieties of magnetite show signs of magnetism, lodestone is the only one
that displays a distantly North-South polarity. Since lodestone is created naturally, it has been known as
early as 600BC. There were observations made by Greek herdsmen that found their iron shod staffs
would get stuck to some of the stones where their herds grazed. Greek philosopher Thales of Miletus
had noted this attraction of iron and hypothesized that this phenomenon occurred because the
lodestone possessed a soul.
The Chinese made the first compasses around 400 BC, which making use of lodestone and shaping it
much like a ladle, sat on a flat board that referred to as a “south pointer” which was originally used for
divinity purposes – showing the way through life. Later on, the Chinese started using the compass for
the purpose of travel. With the “lodestone-compass” able to make use of the Earth’s magnetism, it
always gave a point of reference of which direction was north and south. As the compass became more
developed, explorers were able to better navigate the seas with more accuracy.
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Magnetism
How lodestone is created was looked at by Dr Wasilewski from NASA. Dr Wasilewski hypothesized that
these stones had become magnetized when they get struck by lightning. The quick electrical discharge
from the lighting causes the stone to become magnetic. Dr. W tested his hypothesis with a testing
experiment at a laboratory in New Mexico where they specialize in lighting studies. He successfully
demonstrated that lightning was able to magnetize lodestone with the right composition as he
predicted.
The name magnet comes from lodestones found in a region of ancient Greece called Magnesia.
Now you have seen how magnets can interact at a distance with other
magnets. Similar to the interaction of with the Earth with other objects—it
be felt at a distance. Can you determine the direction of the interaction of the
on other objects? How? Using a compass we can do a similar experiment to
determine the direction of a magnetic field. Observe the way a compass
points at different positions around a bar magnet and mark it on a piece of
paper.
can
Earth
What do you notice?
What patterns do you observe?
Now the students should have made a hypothesis that magnets have an invisible agent of interaction
(magnetic field) where it can interact with object at a distance without having to directly touch them.
They should also mention that this field has a direction (polarity) and similar directed fields repel and
dissimilar attract. Here is a place where we can add in the observation experiment of the iron filings. I
agree we should do the iron filings here and follow up with the
statement about Faraday’s magnetic field concept. We should
definitely tell them not to use the term for granted but actually
question WHAT the magnetic field concept is? HOW do we
describe the field? I’m thinking the iron filing experiment would
go
best here as they can now actually see the field.
A field line is a locus that is defined by a vector field and a starting
location within the field. A vector field defines a direction at all points in space; a field line may be
constructed by tracing a path in the direction of the vector field. More precisely, the tangent line to the
path at each point is required to be parallel to the vector field at that point.
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Magnetism
Field lines are useful for visualizing vector fields, which consist of a separate individual vector for every
location in space. If the vector field describes a velocity field, then the field lines follow stream lines in
the flow. Perhaps the most familiar example of a vector field described by field lines is the magnetic
field, which is often depicted using field lines emanating from a magnet.
A complete description of the geometry of all the field lines of a vector field is sufficient to completely
specify the direction of the vector field everywhere. In order to also depict the magnitude, a selection of
field lines is drawn such that the density of field lines (number of field lines per unit area) at any location
is proportional to the magnitude of the vector field at that point.
Observe the orientation of a compass by a wire where the current is turned on and off. Pay careful
attention to the direction of the compass before and after the current is turned on. Where else have you
seen a compass move without direct physical interaction?
Use the compass to draw lines to describe the interaction of the compass around the wire with the
current flowing in one direction. Then again in the other direction. What do you notice is different
about this interaction versus the interaction before with bar magnets?
Now, students repeat the process with a current carrying wire instead of a bar magnet. They use the
compass to help them draw the direction of the field and then will in the next section use that interaction
with the compass to create a hypothesis.
13
Magnetism
Ørsted story
Before 1820, the only magnetism known was that of iron magnets and of lodestones.
This was changed by a little-known professor of science at the University of Copenhagen,
Denmark, Hans Christian Ørsted.
In 1820 Ørsted arranged in his home a science demonstration to friends and students.
He planned to demonstrate the heating of a wire by an electric current, and also to carry out
demonstrations of magnetism, for which he provided a compass
needle mounted on a wooden stand.
While performing his electric demonstration, Ørsted noted to
his surprise that every time the electric current was switched on,
the compass needle moved. He kept quiet and finished the
demonstrations, but in the months that followed worked hard
trying to make sense out of the new phenomenon. But he
What Ørsted saw.
couldn't! The needle was neither attracted to the wire nor
repelled from it. Instead, it tended to stand at right angles (see drawing below). In the end he published
his findings (in Latin!) without any explanation.
Observe two compasses placed at different points around a wire loop of wire.
Is there anything different about the direction of the interaction versus the direction of the current?
Can you develop a mechanism to relate the direction of the current to the direction of the compass
around the loop of wire? Hint: look at your hands.
Remember that the compass indicates the existence of a magnetic interaction. First the interaction
between bar magnets and the compass needle, then with the current carrying wire. Can you use these
observations to relate and explain the reaction of the compass in both cases?
Before we did not specifically specify that the direction of the current was important. Here, the
introduction of the loop strongly emphasizes the
direction and the associated direction. Through this
observation experiment, students can see from the
earlier
drawings that the direction of the current greatly
matters
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Magnetism
because it directly relates to the direction of the magnetic interaction.
Developing the idea that the direction of the current is directly related to the direction of the magnetic
we lead them to the development of the right hand rule for forces magnetism (it is time to introduce
magnetic field concepts)
Develop a testing experiment (give a hint: if compass interacts with a magnet and a wire carrying
current – what does it tell you?) for your previous hypothesis developed in part five.
Describe your experiment and make a prediction on the outcome of the experiment based upon your
earlier explanation.
Did the outcome of the testing experiment match your prediction?
If not, why not? If necessary revise your hypothesis.
Students should focus developing a testing experiment to see if the field around a wire is magnetic in
nature. We should guide the students towards seeing if a wire with a current interacts with a magnet.
Following this we should show the video of a wire “jumping out of a horseshoe magnet”. Here their
explanation from earlier should include that a current carrying wire produces a magnetic field. Their
prediction for this testing experiment in the video should predict that if a current carrying wire
generates a magnetic field like a magnet, then it should interact with a magnet when current is
passed through the wire. (Here we should only show the wire jumping; next we will use the wire
jumping and the second part with the wire being pushed down in the next step to help develop the right
hand rule for forces.
Now after Ørsted made and published his discovery these were very much incomplete theories and
observations which didn’t have any kind of conclusive remark or explanation of the effect that you just
saw. So who did the later work? A lot of it was completed some say stolen by Andre Ampere. Born in
1775 he was schooled very much by his father a district judge at the time. His father was very loving,
teaching young Ampere Latin, mathematics, and pushed him to pursue science, and because of this they
say he was very gifted and even a prodigy while very young. He learned about Orsted’s experiments in
the early 1820s and through that began developing his own theory of electricity and magnetism which
greatly contributed to research in that field. His paper: Memoir on the Mathematical Theory of
Electrodynamic Phenomena, which was published in 1826 was considered the most influential on the
15
Magnetism
topic. It was said this lead to discoveries of such scientists such as Faraday, Weber, Thomson, and
Maxwell.
Unfortunately despite all these wonderful accomplishments Ampere lived a very sad life. His
father, whom he really loved, because he taught Ampere all about Latin, math, and pushed him to aspire
was politically affiliated with the wrong group and had his head chopped off during the French
Revolution. Then when Ampere married for the first time, his wife fell very ill and died. Then when he
got remarried the marriage was unsuccessful and made Ampere unhappy even further. And this is all
during his life which he lived to be until he was around 60! Note that the average age was only about 30
years in the 17th and 18th century and he lived for that long. And he was SAD for that long. Can you
imagine? So next time you are teaching or learning something about electromagnetism and you feel a
bit sad, it’s okay to. Ampere was sad all his life so it’s ok for you to be just a little bit depressed when you
study magnets and electricity.
In the previous video you saw the interaction between the wire and a magnet through the fields they
generated. Here we are going to watch it one more time and take careful note of the direction of the
current, the direction of the magnetic field, and the direction where the wire moved.
In the two parts of the video, the only difference was the change of direction of current. How could you
tell in which direction the current was? How can you tell which direction the magnetic field was? In
which direction the force of interaction of the magnet on the wire was?
Use these observations to develop a mechanism to relate direction of the force, direction of the
magnetic field, and direction of the current. Hint: This is similar to what you did in part 4.
In this step we need to be careful to show the videos two parts and make sure the students understand
the directions of the field, current, and force. In the video the red end of the horseshoe magnet is North
and we can determine the direction of the current by the colored leads.
After parts 4 and 7 they should have both right hand rules one for the fields and another for the force.
After they have developed these rules they can now apply them in the next experiment.
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Magnetism
Now apply what you know about currents going
through wires in this next experiment. In this
experiment we have one wire where we know the
direction of the current and a second wire where we
do NOT know the direction of the current. Use the
knowledge and mechanism developed earlier to
determine the direction of the current in the second
wire without looking at the leads like before.
In one wire we show the students that we know the
direction of the current. In a second wire, we hide the direction of the current. During the experiment
we flip the switches and the wires will either attract or repel. Working backwards with their existing
knowledge of how the wires should interact depending on the current, they can infer the direction of the
current in the second wire without actually having to look at the wires and where they touch on the
battery.
The transition now is to direct the students to quantify the relationship between the magnetic
field, current, length of the wire, and the force exerted upon the wire by that field
Now that we know wires carrying current inside a magnetic field have a force exerted upon them,
consider the following data from an experiment similar to one shown to you in the following video.
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Magnetism
Here we show the video of the magnet on the scale and the readout changing after current is passed
through the segment of wire within the horseshoe magnet’s prongs.
F (force)
B (magnetic field)
I (current)
L (length)
1
1b
1
1
2
1b
2
1
2
1b
1
2
½
1b
1/2
1
½
1b
1
1/2
4
1b
2
2
2
2b
1
1
4
2b
2
1
4
2b
1
2
1
2b
1/2
1
4
2b
1
2
8
2b
2
2
In this experiment we have the measured the force exerted by the wire on the horseshoe magnet (F),
the current passing through the wire (I), and different lengths of the wire (L). Note that we cannot
measure the magnetic field (B) directly at the moment. However, we know from our earlier experiment
that B varies due to the inverse squared of the distance. Having a magnet but placing it farther away or
closer to the wire we can double the original field strength (b) without actually knowing the strength of
the original field.
What are the independent and dependent variables?
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Magnetism
Can you quantify the relationship between the force, magnetic field, current, and wire length into a
mathematical relationship?
Now we use this “massaged” data to help them develop the final concept of a quantifiable relationship
between the force, magnetic field, current, and wire length. In this part it’s important to tell the students
that at the moment we cannot currently directly measure the magnetic field. We can however, remind
them of their previous experiment where they see the magnetic field is dependent on distance. This way
similar to the previous lesson with charge they can derive the mathematical relationship without having
to take the idea of the units of magnetic field at face value.
As closure we will go over the four main topics that the students learn.
Magnets interact with other objects at a distance and the strength of that interaction depends on the
distance.
This interaction is due to what we call the “magnetic field”. This field has a direction which can be
determined by using a compass.
Wires carrying a current generate a magnetic field around the wire which can be described qualitatively
with the right hand rule for fields.
Wires carrying a current when in an external magnetic field will interact with the field and have a force
exerted on the wire by the field which can be described qualitatively by using the right hand rule for
forces. In addition, This force of interaction between the field and the wire can be quantified using the
relationship of F = IBL
All student suggestions should be steered toward these four main ideas that were developed throughout
the lesson.
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Magnetism
Chapter 4 Biographies
André-Marie Ampère
Born in 1775 he was schooled very much by his father a district judge at the time. His father
was very loving, teaching young Ampere Latin, mathematics, and pushed him to pursue science,
and because of this they say he was very gifted and even a prodigy while very young. He
learned about Orsted’s experiments in the early 1820s and through that began developing his
own theory of electricity and magnetism which greatly contributed to research in that field. His
paper: Memoir on the Mathematical Theory of Electrodynamic Phenomena, which was
published in 1826 was considered the most influential on the topic. It was said this lead to
discoveries of such scientists such as Faraday, Weber, Thomson, and Maxwell.
Unfortunately despite all these wonderful accomplishments Ampere lived a very sad life.
His father, whom he really loved, because he taught Ampere all about Latin, math, and pushed
him to aspire was politically affiliated with the wrong group and had his head chopped off during
the French Revolution. Then when Ampere married for the first time, his wife fell very ill and
20
Magnetism
died. Then when he got remarried the marriage was unsuccessful and made Ampere unhappy
even further. And this is all during his life which he lived to be until he was around 60!
Michael Faraday
In September of 1791, Michael Faraday was born into a large family in Surrey, England.
Faraday’s father was a blacksmith and was unable to send his son to school, so Michael went to
work as an apprentice for a bookbinder where it allowed him to read to his heart content. He was
particularly interested in reading about chemistry and magnetism. In 1812, Faraday started to
attend lectures of Humphrey Davy who eventually hire Faraday to work in his lab as an assistant.
When Hans Christian Ørsted made his discovery of an electric current produces a magnetic field
in 1820, this lead Faraday to the invention of the electric motor. Faraday then took the spinning
motor further by setting up a second loop of wires to a galvanometer and found just like Ampere,
that current flowed in the second wire when the switch on the first loop was turned on or off.
Unlike Ampere who just dismissed this observation, Faraday hypothesized that the changing
magnetic field caused the electric current in the wire and lead to the principle of electric
induction. In 1831, Michael Faraday built upon another experiment, this time one by Dominique
Arago where he discovered a rotating copper disk deflected a compass needle. Faraday was able
produce a continuous current with his set up and invented the first electric generator. In 1839,
Faraday suffered a mental breakdown from which he never fully recovered and passed away in
1867.
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Magnetism
C.H. Ørsted
Hans Christen Orsted was born in 1777 to a father who owned a pharmacy. Hans and his brother
received most of their early education at home before they headed to Copenhagen and took the
entrance exams at the University of Copenhagen. Hans excelled at the university and in 1801 he
was awarded a traveling scholarship that allowed him to travel to Germany and France for three
years meeting with various scientists in his travels. In 1806, Hans became a professor at the
University of Copenhagen conducting research with electric currents and acoustics. He also
started the studies of the physical science and research laboratories. Hans married Brigitte
Ballum and had five daughters and three sons. When Hans was setting up for an observational
experiment for his friends in 1820, he noticed that a compass was being deflected in direction
when he turned the flow of current through a wire on and off. He hypothesized that an electric
current produces a magnetic field. Hans later did some follow up test experiments, observing the
compass needle pointed perpendicular to the wire and when the current direction was reversed,
the compass needle reversed direction also. He later published in finding in Latin.
22