Science 2201 laboratory
Go to the PhET link, click on simulations, then click on “Electricity, Magnets & Circuits” and click on the “Faraday’s
The first tab shows a magnet and a compass like shown in th
e Figure. The magnet results on a
magnetic field. This is represented by the small compasses shown throughout. The stronger the magnetic field, the brighter ar
the small compasses. The larger compass can be used to visualize the effect of the magnetic fie
ld on a small magnet (the
magnet of the compass).
north pole of the bar magnet attracts the south pole and attracts the north
pole of the compass. The strength of the magnetic field diminishes as you move away from the magnet
Now go the simulations at KSU and try the four simulations labeled as Electrical Fields. Which of these simulations provide a
field similar to the one observed with a magnet?
simulation “Electric Field 3” shows a similar field patter as the pattern
the bar magnet. When you press the “Field vectors” button, like the small compasses, arrows representing the electrical field
point away from
the positive charge and
towards the negative charge.
Use the provided magnet and iron fillings
to observe the effects and shape of the magnetic field. Describe what you observe.
align in the same direction as the magnetic field. Each of the iron bits acts as a small compass.
An experiment a little exp
nsive to p
erform would consist of breaking up magnets and showing that whenever we break a
magnet with a north and
south pole, we obtain two magnets each having a north and a south pole.
So far, we cannot observe
a north pole or a south pole by itself.
That is par
tly because each magnet we observe is actually made up of tiny magnets, the
smallest of which is the electron. In a larger scale, the bar
magnets like the ones we are using are made up of materials that are
called ferromagnetic. Iron is an example of a fer
romagnetic material. The simulation titled “Magnetic Domains” illustrates
this concept. It shows a piece of ferromagnetic material that we can subject to an outside magnetic field. Initially, the
magnetic field is zero, the magnetic domains are oriented at
Check it out; how many of the domains are oriented
towards the right and how many are oriented to the left?
About an equal number are oriented in each direction. The difference, when it
, is tiny.
Use the slider to impose a positive magneti
c field and repeat the count. How many of the domains are oriented towards the
right and how many are oriented to the left?
More domains are oriented towards the right.
Use the slider to impose a negative magnetic field and repeat the count. How many of t
he domains are oriented towards the
right and how many are oriented to the left?
More domains are oriented towards the left.
What do you conclude?
Domains are originally pointed in random directions. When you subject them to a magnetic field, they orient
same direction as the field.
Go back to the PhET “Faraday’s Electromagnetic Lab” simulations. Click on the “Electromagnet” tab. You should observe
something similar to what is in the Figure. Describe what you observe and compare it
to what you have observed with a bar
The magnetic field pattern is the same as the magnetic field pattern due to a bar magnet. In this case (the default) the righ
side of the coil acts as a north pole.
Use the slider on the battery to chang
e the type of current flowing through the coil. (1) What happens when the current is
reduced? (2) What happens when the current is zero? (3) What happens when the current is reversed?
(1) The strength of the
magnetic field diminishes, (2) the coil stops fr
om acting as a magnet, (3) the poles are reversed, the right hand side of the coil acts now as a
Click on the “Pickup Coil” tab. You should observe something similar to what is in the Figure.
You can move the coil or the
magnet; you can also change the strength of the magnet and flip its polarity. You can change the loop area and the number of
loops. Make all of these changes, one at a time
Which of these changes result in the light bulb giving off light?
All of these
nges result in the light bulb giving off light.
ELECTRICITY AND MAGN
For how long does the bulb give off light?
The light bulb gives off light only when the change is occurring.
What do you conclude (seek help from the instructor in discussing magnetic flux.)
The light bulb
gives off light whenever a change
of magnetic flux occurs. The amount of light produced depends on the amount of flux change and the rate at which this change
faster the change, the more light is giving off.
lick on the “
” tab. You should observe something similar to what is in the
illustrates the concept of a transformer.
You can move
; you can also change the
current through one of the
and flip its polarity. You
can change the loop area and the number of loops
for each of the coils
Focus on changing the
current through the first coil and describe what you observe? Does the light bulb give off light when you are not in the proc
of changing the current?
ht bulb in the second coil gives off light whenever the current in the first is being changed. No light is
off when the change stops.
Change the battery now into an AC Power supply. Use the slider in the bottom of the supply unit to change its fre
the slider to the right, to change the voltage. Describe what you observe. Can a transformer be used with circuits powered wi
The AC power source results in the light bulb giving off light the whole time. However, as the AC current
alternates, the light in the
light bulb flickers. A transformer can be used only with AC currents. Due to their alternating nature, AC currents result in
changing magnetic flux. That is why they result in the light bulb giving off light. Bat
tery powered circuits do not result in a change in the
magnetic flux. Thus, a transformer does not work for DC (battery powered) currents.
Now click on the “Gen
rator” tab. You should observe something similar to what is in the Figure
. This simulation illustrates
the concept of an
electric generator. You can change the strength of the magnet,
the loop area and the number of loops for
You can also regulate the amount of water flow. Manipulate, one at a time, each of the parame
ters, and describe in your
own word the recipe for producing electricity.
Can you think of another method for producing electricity not relying on the
flow of water?
All what is needed to produce electricity is to change the magnetic flux through the coil.
The factors that contribute to higher
power output are: (1) strength of bar magnet, (2) number of coils, (3) water flow level.
Instead of water, any mechanism capable of rotating to
bar magnet will work.
Use the provided kit to build an
d run the electrical motor. Try to explain how it works in terms of magnets attracting and
Ask your instructor for help.
Because of the way the wire is stripped at the end, the coil acts as an electromagnet during half
of the turn and as a non
agnet during the half. During the half turn it is magnetic, the coil gets attracted to the pole of the magnet
sitting on top of the battery)
gaining rotational speed in the process. As it turns, it stops from being attracted
to the magnet but keep
rotating because of inertia. Once it makes another half turn, it is powered again. This means that it acts again as an electr
omagnet and is
attracted again to the magnet.