Faraday’s rotating wire – the
homopolar motor: time to update?
Geoff Auty
ABSTRACT Answering some of the questions raised in the production of a previous article led to
the development of a simple alternative design for the rotating wire demonstration. Significantly,
this demonstration avoids the use of mercury as a conducting liquid. The attempt to explain
variations in performance of another model and seeking the best performance for a new one
became a catalogue of theoretical and practical activity that illustrates ‘How science works’. Much
modern science requires the investment of extensive research facilities and involves large teams of
people. Yet, as in Faraday’s time, the work described here could be done in a school laboratory or a
garden shed. To see only the successful outcome, look at Figure 3 and the description linked to it.
Introduction
Consideration of the possibility of updating
an instructive demonstration, which had
become defunct owing to health and safety
issues, occurred when I was asked questions
about understanding a modern alternative. The
subsequent thinking processes, the investigations
and the eventual building of a viable
demonstration became a convincing example
of ‘How science works’. I believe that the final
result is worth recording in detail, even though a
simple description of what worked would take up
much less space. It is tempting to do just that, and
to pretend I got it all right first time. However, I
admit to a number of ill-considered theories and
false trails that I believe truly record the path of
progress in demonstrating ‘How science works’.
The story of this development began when
Alan Goodwin sent a proposal for a Science note
in School Science Review (Goodwin, 2009).
After trying to explain some investigations into
the performance of his method, which involved a
rotating magnet, he felt that several features were
unclear. In my capacity as Editor of SSR, I discussed
a number of points of theory with him but eventually
it all had to be put to the test. It would help to look at
that method to understand the reasons behind some
of the discussions that follow in Boxes 1–3.
The route to success in that rotating magnet
method, which involved just a 1.5 V cell, came
from the strength of a modern neodymium magnet
that was obviously not available in Michael
Faraday’s time. I went on to use the same magnet
to adapt Faraday’s design. I found success more
quickly than I had dared hope. Whether this was
due to luck or judgement, I felt that many things
had to be checked and justified in order to claim
that the design was reproducible.
History
In the past, physics teachers may have
demonstrated the Faraday rotating wire
experiment (Abbott, 1977; Licker, 2003). An
important part of the original method was the
use of mercury as a conductor (Figure 1), which
allows motion without loss of electrical contact.
Figure 1 Wire loosely suspended in a glass tube
and dipping into mercury
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Physics teachers may also have demonstrated
setting up a mercury barometer and coped with
broken mercury thermometers numerous times.
Indeed, it was quite common to pass a bottle of
mercury around the class so the students could
feel how heavy it is. We are all still here to tell the
tale, but fears about the toxicity of mercury have
caused it to be withdrawn from use in schools
and these opportunities are no longer available.
Students no longer have the opportunity to see
globules of this fascinating liquid metal run across
a glass sheet.
The logic of the rotating wire experiment is
that the wire suspended from another in a glass
tube is just dipping into the mercury but is free to
move. When the current is switched on, this wire
rotates around the magnet.
The basic explanation is found by considering
the view at the level of the top of the magnet
(north pole in this case), as in Figure 2.
Seen in this top view, the flux lines (which
represent the direction of the magnetic field) are
away from the north pole and are hence radially
outwards. The flux lines eventually go to the south
pole of the magnet, but that is a long distance
behind the plane of this diagram. This is why
Faraday chose a long slim magnet.
Considering two of many possible positions
for a wire carrying current downwards (which
Figure 2 Cross-sectional view at the top of the
magnet. Two positions for the wire are shown, with
enlargements illustrating the direction of motion
(the × symbol in the wire indicates that the current
is flowing into the diagram). Asking students to
consider the wire in other places around the magnet
will establish the explanation of a circular motion
116 SSR September 2010, 92(338)
means into the plane of this diagram), the
application of Fleming’s left-hand rule shows
that the movement of the wire at any point is in a
tangential direction. Hence it moves in a circle –
clockwise in this case – but reverse either the field
or the current and it will move anticlockwise.
The two wires hooked together at the top
allow free movement but retain electrical
contact. The bottom of the loose wire moves
in the mercury, the liquid metal enabling good
conduction to the wire and providing the negative
connection to a wire through the bung at the
bottom of the tube.
This arrangement is the simplest observation
of continuous rotation available using the electric
motor effect but is of no commercial value. It is
sometimes called the homopolar motor because the
free wire always moves around just one pole. Once
mercury was removed from the school environment,
this demonstration was abandoned – until now.
For further information on Michael Faraday
and this historic demonstration, see the references.
In this proposed method, the availability of
the very strong neodymium magnet means that
a demonstration based on the same principle as
Faraday’s rotating wire is possible without the use
of mercury. However, in the method described in
Alan Goodwin’s note, it is the magnet that rotates
rather than the wire. In our correspondence,
Alan asked several questions about clarifying
the explanation of his demonstration and
making it successful. Answers to these enhance
understanding of the viability of electromotive
demonstrations and are given in Boxes 1–3.
Recreating the Faraday design
The basic apparatus to recreate the Faraday design
is illustrated in Figure 3.
A short wooden rod with a diameter just large
enough for it to fit tightly inside a piece of copper
tube (scrap remaining from a plumbing project)
was fixed to a baseboard.
A steel screw was fixed into the centre of the
top of the rod and the neodymium magnet was
placed on the head of the screw.
The piece of copper tube was pushed onto the
rod, trapping a piece of wire. The top of the tube
was approximately level with the top of the magnet.
While it is not critical, the top of the tube should
preferably not be below the centre of the magnet.
Two pieces of wire had their ends bent into
open hook shapes. One became the rotatable wire
Auty
Faraday’s rotating wire – the homopolar motor: time to update?
More importantly, this apparatus operates without
mercury.
I was so excited by this instant success
that I called my wife to the shed to witness
the observation. She was reluctant as she was
busy cooking the Saturday evening meal but
I recounted reports that, according to legend,
Michael Faraday had first called his wife from
preparing the Christmas dinner to see a similar
discovery. So there was a precedent.
Was this a lucky accident? Could it be done
better? More research was needed to ensure this
success was reproducible.
Researching the design
Figure 3 Apparatus to create the layout of a
mercury-free version of Faraday’s rotating wire
to hang from the other. The second (supporting)
wire was held in a clamp. Apart from the curve for
the hook, the suspended wire should be as straight
as possible.
The free ends of the supporting wire and
of the wire trapped at the bottom of the copper
tube were connected to a dc power supply via an
ammeter (not essential, but I found it useful to
monitor the current).
Once the apparatus was assembled and
connected, the bottom of the suspended wire
immediately began to rotate around the top of the
copper tube. Having such a strong magnet meant
that a long slim magnet, as usually illustrated in
the Faraday method, was no longer necessary.
Two copper tubes (15 mm and 22 mm diameter)
and three suspended wires were tried (Table 1).
Supporting wires of the same type were also tested.
I thought it worth testing whether the
demonstration would be easier to observe
with a 22 mm diameter tube (Table 2) than
with the 15 mm tube used in the first attempt
(Table 3). I also decided that I should take
some measurements of current and potential
difference (pd). While these are not extensive,
they do provide sufficient detail to understand
the performance. As contact was not always
consistent, the ammeter readings were often an
estimate of an average value.
The other observations in Tables 2 and 3
are not described with consistency because the
performance was so varied. In fact, the limits
of success are as important as success itself. To
assess the rate of rotation, I timed ten revolutions
for each successful operation. In the tables, the
columns headed T/s indicate the time taken for ten
revolutions when running successfully.
It will be apparent that, having pushed this to
various limits, I might seem to be playing with
too many variables, and much more research
could be done.
Table 1 Types of wire used in tests
Wire type
Stiff single
Three-strand
Multistrand
Description
A piece of copper wire 1.8 mm in diameter; no plastic sleeve
A section of wiring cable with three strands each of 0.9 mm
diameter in a plastic sleeve
A section of flexible cable with 14 strands of wire each of
0.2 mm diameter, making an overall diameter of 1 mm when
twisted together
Length of suspended wire
9 cm
15 cm
15 cm
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Table 2 Observations with a 22 mm diameter copper tube
Suspended wire
Meter readings
T/s Observations
pd/V Current/A
Support wire – three-strand
Three-strand
3
6
2.4
2.4
8
–
3
6
3
6
2–3
2–3
0.3
0.4
–
–
8
8
Works
Wire swings out, ammeter fluctuates; runs but liable
to stick
Sticks a lot
Reasonably successful, not consistent
Runs around steadily, slight swing-out*
Runs around steadily, more swing-out
3
6
10
3
6
3
6
0.4
0.4
1.3
2.2
2.0
0.2
0.2
7
7
8
–
–
–
–
Runs quite smoothly
Runs quite smoothly
Runs but scrapes noisily
Sticks
Sticks at times
Runs only if suspension is carefully centred
Runs easily but bounces
Support wire – multistrand
Three-strand
3
6
Stiff single
3
6
Multistrand
3
?
0.6
0.4
0.6
0.3
–
6
–
–
7
6
0.4
7
Poor – sticks, current inconsistent
Runs quite well
Not successful
Reasonable rotation but current shoots up if it sticks
Swings out somewhat but smooth; runs successfully
if well centred
Very stable rotation
Stiff single
Multistrand
Support wire – stiff single
Three-strand
Stiff single
Multistrand
* ‘swing-out’ means that the wire swings away from the copper tube noticeably and then drops back and touches again,
enabling motion to continue
One point to note is that, even for steady
rotations using the same set-up, current and pd are
not proportional. The reason is that an increase in
current results in an increase in force, producing
a faster rotation. In turn, this produces a back
electromotive force (emf) that restricts the current.
The consequence is that there is only a small
increase in current and the rate of rotation for a
substantial increase in pd. The effect of back emf is
also particularly noticeable if the wire ‘sticks’ (stops
moving and remains in contact with the tube). The
current then increases considerably because there is
no significant resistance in the circuit.
Enhancing the design
As illustrated in Figure 4 (which is similar to
Figure 2), application of Fleming’s left-hand
rule shows that the force on the movable wire is
tangential to the copper tube wherever it makes
contact.
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Figure 4 Cross-sectional view where the movable
wire touches the tube (the × symbol in the wire
indicates that the current is flowing into the diagram)
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Faraday’s rotating wire – the homopolar motor: time to update?
Table 3 Observations with a 15 mm diameter copper tube
Suspended wire
Meter readings
T/s Observations
pd/V
Current/A
Support wire – three-strand
Three-strand
3
6
Stiff single
3
6
Multistrand
3
6
Support wire – stiff single
Three-strand
Stiff single
Multistrand
3
6
3
6
10
3
6
Support wire – multistrand
Three-strand
3
6
Stiff single
1.5 3
6
Multistrand
1.5
3
6
0.4
0.6
–
–
0.2
0.2
7
7
–
–
8
8
Steady rotation (some ammeter fluctuation)
Swings out more
Sticks
Sticks
Consistent rotation
Swings out much more, about twice per revolution;
hardly seems to touch tube – looks almost like if
‘floats’ without contact
0.2
0.1
0.5
0.1
0.16
0.2*
0.2
7
7
6
6
5
–
–
Consistent rotation
Swings out as it rotates
Fairly stable rotation, swings out slightly
Good rotation
Good rotation (no swing)
In both cases, swings out so much that the wire
hardly touches the tube; looks like magic, defeats the
reason for doing it
0.2
0.3
1.6
0.6–1
0.6–0.8
0.04
<0.1
0.14
8
7
–
7
7
8
7
–
Rotates easily, about one touch per revolution
Jumpy, about one touch per revolution
Sticks
Long contacts, large jumps
Large swings
Decent rotation
Only about one touch per revolution
Swings wildly but keeps going
* best estimate (fluctuating wildly)
When the current is switched on, the tangential
direction of the force causes the wire to move
away from the surface of the copper tube. If it
succeeds, the current stops and the force reduces
to zero. The wire will then fall back to the copper
tube, making contact in a different place. In this
way, the wire can move in a series of bounces,
repeatedly touching and leaving the tube.
The weight of the movable wire as it leans on
the tube tends to make it stay in contact. Hence,
for some of the arrangements described in the
tables, smooth motion is obtained with small
currents but the movement becomes erratic if the
current is increased.
So, is it possible to obtain an increased speed
and a smooth movement? In an attempt to prevent
the wire swinging away from the tube, 15 mm
and 22 mm tubes were arranged concentrically
(Figure 5). The suspended wire was arranged to
run in the gap between the tubes. The tubes were
electrically connected so that current would flow
when the wire touched either of them. The logic
for this extra connection was that the effect of
briefly touching the inside surface of the outer
tube would help the circular motion to continue.
I obtained some movement with this design,
but it was not particularly successful. There were
two problems. Firstly, the gap was too narrow
for my wires. They fitted into the space available
but kept jamming during movement. Secondly,
the tangential force encouraged the wire to press
against the inner surface of the outer tube, and this
effect possibly inhibited free movement.
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Figure 5 Apparatus with concentric copper tubes
Figure 6 Apparatus with concentric tubes from a
22 mm copper tube and a 35 mm film container
With a slim wire of suitable flexibility, I
believe this method could be more successful, but
I did not pursue it further.
As explained, the gap between the tubes was
too narrow to allow all the wire types to run
freely. Also, having the electrical connection to
the outer tube is probably not significant. For
wires travelling around the outside of a single
piece of tube, observations show that the 15 mm
tube is slightly more reliable, but motion around
the 22 mm tube is easier to see and, with the wider
angle, the whole effect is more convincing. Hence,
another option was to use the 22 mm tube with a
plastic outer tube to contain any ‘bounce’ but not
contribute to providing the transverse force.
Although any plastic tubing of similar
diameter (30–35 mm) would suffice, I tried a
plastic 35 mm film container with a diameter of
30 mm. I cut a large hole in the bottom of the
container to make a push-fit onto the 22 mm
copper tube, but it would perhaps be as easy to
start again by drilling a small hole in the bottom
of the container, provided that the length of copper
tube makes for a compatible height. However,
an extra hole would be needed for the electrical
connection to the copper tube. This arrangement is
illustrated in Figure 6, with the results in Table 4.
Figure 7 shows the assembled apparatus with
a 15 mm tube, and various other parts used for
the tests.
Illustrating the field pattern and ‘strength’
of the magnet
120 SSR September 2010, 92(338)
Illustrating the magnetic field pattern around the
magnet (particularly the radial field away from the
top surface) using iron filings is another idea to
explore. This can emphasise the shape of the field
in three dimensions and increase understanding
compared with two-dimensional diagrams in
books and in this article. These demonstrations are
quite spectacular with these strong magnets but
take care to find a method which ensures that iron
filings do not get onto the magnet itself – they will
be very difficult to remove.
I have suggested methods for displaying
magnetic fields in previous articles in SSR (Auty,
1968; 1994). In this case, I found a rectangular
plastic tray 24 cm by 18 cm. A sheet of A5 paper
fitted well in the base. I placed a short plastic tube
of diameter 30 mm on the paper and sprinkled iron
filings into the tube. The iron filings remained in a
circular heap when the tube was lifted away. Holding
the tray carefully in one hand, I used my other
hand to place the magnet beneath the tray. When
it was underneath the iron filings, they produced a
magnetic field pattern in three dimensions (Figure 8),
and the strong attractive force caused the magnet to
cling to the underside. For viewing, the tray could
then be placed on a bench on small wooden blocks.
To obtain a two-dimensional pattern, I placed
the magnet beneath a piece of plywood about
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Faraday’s rotating wire – the homopolar motor: time to update?
Table 4 Observations with a 22 mm diameter copper tube inside a plastic 35 mm film container with a
diameter of 30 mm
Suspended wire
Meter readings
T/s
pd/V Current/A
Support wire – three-strand
Three-strand
6
10
Stiff single
3
6
Multistrand
3
6
10
Support wire – stiff single
Three-strand
Stiff single
Multistrand
3
6
10
3
6
10
3
6
10
Support wire – multistrand
Three-strand
3
6
10
Stiff single
3 6
10
Multistrand
3
6
10
0.6
2.4
0.4
0.6
0.2
0.2
0.4
7
9
9
8
9
9
–
Runs successfully
Sticks slightly at times, scrapes audibly
Reasonable rotation
Reasonable rotation
Reasonable rotation
Reasonable rotation
More likely to stick, jump and spark
–
~2
~2
–
~2
~2
–
0.6
0.6
–
12
12
–
–
12
–
7
8
Unsuccessful
Runs reasonably but can stick
Runs better but not perfect
Unsuccessful
Runs inconsistently (sticking often)
Runs adequately, scrapes audibly
Unsuccessful
Runs well
Runs better; slower, but a more consistent movement
–
2.2
0.6
2.2
1.6
0.6
~0.8
0.6
0.6
–
–
–
–
12
12
–
7
6
Unsuccessful
Poor; sticks yet conducts
Poor; sticks yet conducts
Tends to stick
Runs successfully
Runs but sticks occasionally
Rotates inconsistently; current jumps
Runs successfully
Runs successfully
5 mm thick and sprinkled iron filings very thinly
onto the paper in the tray. I then carefully lowered
the tray into position above the magnet. Very
gentle tapping of the paper achieved the pattern
shown in Figure 9. Without the plywood spacer,
the iron filings would be attracted too strongly
towards the magnet across the paper (resulting
in a smaller version of the pattern in Figure 8)
and the extent of the field pattern away from the
magnet would not be so easy to see.
contact with the powerful magnet and could attach
itself to the steel casing of a leakproof dry cell,
making a point contact (Figure 10).
As soon as the flexible wire is allowed to
touch the smooth surface of the magnet, the
magnet spins with the point of the screw acting
as a freely moving bearing. Three questions
were discussed between Alan Goodwin and me
to consider the working of this method and the
possible ways to improve it:
Further thoughts from reconsidering the
original article
1 Does the position of contact of the wire onto
the side of the magnet affect the direction of
rotation?
2 Does the direction of contact affect the
rotation?
In the method previously published (Goodwin,
2009), a screw was magnetised by being in
Observations
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Figure 7 Apparatus set up with a 15 mm copper tube and a single 1.8 mm suspended wire. A 22 mm tube
inside a plastic 35 mm film container and the other wires used in the tests are also shown
Figure 8 Radial magnetic field pattern obtained with
the north pole of a neodymium magnet just beneath
a plastic tray (about 2 mm thick) holding the iron
filings, illustrating flux lines outwards and upwards
away from the pole
122 SSR September 2010, 92(338)
Figure 9 Radial magnetic field pattern obtained with
the north pole of a neodymium magnet held by a
wooden spacer about 7 mm beneath the plastic tray
holding the iron filings, illustrating flux lines outwards
from the pole
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Faraday’s rotating wire – the homopolar motor: time to update?
3 Is it possible to arrange this rotation without
the current having to pass through the magnet?
The questions are discussed further in Boxes 1–3.
Conclusion
Figure 10 A magnet suspended by a screw from a
dry cell, with wire available to complete the circuit
I did not try every possible combination,
only enough to show that the effect can be
demonstrated. I only recorded observations that
seemed relevant and there are many other possible
variations, not one ‘right answer’.
My observations show that ‘simplest seems
best’. Success will depend on the mass and length
of the moving wire and its flexibility, and on the
strength of the magnet.
A challenge could be to show that it can be
done and then set students an investigation to see
whether they can improve on the basic design
using the techniques I have begun to pursue or
any others you or they might think of. Further
questions might be considered concerning
Faraday’s initial design. Why did he choose a long
magnet? Without the guidance of a solid surface,
BOX 1 Does the position of contact of the wire onto the side of the magnet affect the direction of
rotation?
In the method described, the magnet (having the shape of a short cylinder) was attached to the head of a
steel screw. The screw was then sufficiently magnetised to be attached to the casing of the dry cell (provided it
contains steel), making a point contact.
To provide the opportunity for various tests, I clamped a small steel plate horizontally and suspended the
magnetised screw from that (Figure 11). I then connected a variable laboratory power supply and included an
ammeter to monitor the current.
Figure 11 Suspension of the magnet to enable testing with a separate power supply and allow the contact
position of the wire on the surface of the magnet to be changed
All positions of contact to the curved side of the magnet seemed to work equally well. Although I did not
perform very careful tests, I think it is possible that contact to the middle will give a slightly faster rotation than
contact near the top.
It was very difficult to establish any rotation when making contact underneath the magnet. Some inconsistent
movement was established with contact near the edge, but not near the centre.
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BOX 2 Does the direction of contact affect the rotation?
From mechanical rather than electrical considerations, the impression could be that contact of the wire against
the cylindrical side of the magnet, as in position A of Figure 12 (with the magnet spinning ‘away’ from the end
of the wire), would provide a more stable contact than positions B or C. To understand this better, consider
contact brushes against a commutator in an electric motor, or sharpening a blade against a grindstone.
Rotation appeared to be equally successful in all positions.
To provide a better opportunity for contact, I then split the end of the flexible stranded wire to make a
Y shape (Figure 13).
Figure 12 Top view showing three possible
contacts for the wire against the side of the
rotating magnet
Figure 13 A Y-shaped contact onto the side of the
magnet: (left) stationary; (right) rotating
The rolling action caused the magnet to move away from one side of the Y-shaped contact, so it was
concluded that this arrangement was not needed.
However, the use of stranded flexible wire to make the contact does seem to be the best choice for this
method.
Although a single dry cell (1.5 V) was successful in the method described by Alan Goodwin (2009), I found
that, at 1.5 V, rotation was not very stable. The ammeter reading fluctuated between zero and 1.1 A as the
contact was frequently broken and remade. If running steadily, it settles to about 0.5 A.
More reliable rotation could be obtained at 3 V. The magnet spinned confidently, with current varying
between 0.4 A and 0.6 A.
Running more smoothly (and quickly) at the higher pd meant that the back emf became more effective.
Hence the current was only about the same as at 1.5 V. It might come as a surprise that doubling the
pd did not double the current. The simple explanation is that, with the relative motion of the magnet and
the wire, the arrangement acted as a dynamo attempting to deliver current in the opposite direction.
Textbooks on Advanced-level physics will give more detail.
BOX 3 Is it possible to arrange this rotation without the current having to pass through the magnet?
The challenge was to arrange a loop of wire
two of the places indicated would cause clockwise
around the magnet and obtain rotation with no
rotation but another two would cause anticlockwise
sliding contact at all.
rotation. The result is no rotation. Hence, with the
movable magnet and fixed wire, there is no rotation.
I could not find any viable method of achieving this
– Figure 14 helps to indicate why not.
The effect at the position where the wire passes
beneath the magnet is to make the wire swing
In all four positions on the sides of the loop indicated
outwards. So the freely suspended magnet within
in Figure 14, black arrows indicate the direction of
this loop of wire will swing in a direction ‘into the
the current and purple arrows indicate the direction
diagram’.
of the magnetic field. The blue arrows then indicate
the direction of force that should, according to
The Faraday method used only the upper half of
Fleming’s left-hand rule, cause motion of the wire.
the magnet. Perhaps that should be considered.
If the wire is held in a fixed position then there is
As will be seen from Figure 15, in which only two
the possibility of motion of the magnet. Maintaining
positions to the sides are relevant, this brings no
attention on the effect on the wire, the forces in
improvement.
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Faraday’s rotating wire – the homopolar motor: time to update?
BOX 3 (cont.)
Figure 14 Indication of current-carrying wire
crossing magnetic flux lines in four positions for
a symmetrical loop close to the magnet, and the
appropriate directions of electromagnetic force
However, in both of the above methods, the
magnet tends to swing – backwards in the
arrangement of Figure 14 and forwards in the
arrangement of Figure 15.
Another consideration might be that, because
there was only one wire in the Faraday method,
the ‘failure’ of the above designs is due to the
attempt to provide symmetrical arrangements. An
asymmetric arrangement is shown in Figure 16.
Once again, all the forces tend to swing the
magnet and wire towards each other. The
asymmetric arrangement means that, in positions
shown on the right-hand side of the diagram,
the wire is in a weaker field (which would imply
smaller forces). However, those forces do not
just exist at the positions shown. They are
spread throughout a much longer part of the wire
carrying the same current (which alone implies
greater force). Even without a full mathematical
analysis, this should explain that the resulting
effect is the same on both sides of the wire so
that there is no imbalance from which rotation
could be derived.
From these considerations, I believe that letting
the curved surface of the magnet slide against the
flexible wire will give the only successful rotation.
Figure 15 Indication of current-carrying wire
crossing magnetic flux lines in two positions for a
symmetrical loop close to the magnet and passing
around at mid-level, and the appropriate directions
of electromagnetic force
Figure 16 Current-carrying wire close to the magnet
at one side but taken away at mid-level at the other
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how did the wire move in a circular path, and
what determined the radius of the path?
Considering that I started by being asked
questions about understanding an existing science
topic, thought of possible theories to explain
behaviour beyond what was published, performed
experiments to put theories to the test, produced a
successful technical outcome to overcome health
concerns, and tested limitations on apparatus
design, I think the process recorded here offers a
valid example of ‘How science works’.
References
Websites
Abbott, A. F. (1977) Ordinary level physics. 3rd edn. p.
447. London: Heinemann Educational Books.
Auty, G. (1968) Demonstration of a magnetic field pattern in
three dimensions. School Science Review, 50(171), 389.
Auty, G. (1994) Old science, new materials. School Science
Review, 76(275), 78.
Goodwin, A. (2009) The simplest electric motor – ever?
School Science Review, 91(334), 33–36.
Licker, M. D. (2003) Faraday rotation experiment. In
Dictionary of physics. 3rd edn, p. 142. London: McGrawHill.
www.phils.com.au/mf.htm
www.sparkmuseum.com/MOTORS.HTM
Geoff Auty is the Editor of School Science Review.
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