AP Physics B Magnetism:
Conceptual Webquest
Magnets are created by
moving charges. ~In a stationary (bar) magnet, the spinning electrons in iron
create the magnetic field. ~In a wire, electrons are flowing through the wire
as current. ~In a third case, charged particles can be moving on their own. ~In
this webquest, we will look at all three situations
and the resulting magnetic fields and forces.
Intro: Basics of
magnetic fields
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html
Click on the link above and read about the basics of magnetic
fields. Answer the following questions as you read:
3. What units are magnetic
fields measured in?
4. Magnetic fields exert
forces on other magnets and on moving charges (because moving charges ARE
magnets)
5. Write the equation
for the force a moving charge will feel as it moves through a magnetic field.
6. Will a magnetic field
exert a force on a stationary charge? Use the equation from question 4 to
explain why or why not.
Part I: ~Stationary
(bar) magnets
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html
Click on the link above
and look at the magnetic field lines produced by a bar magnet
Note the direction of
the magnetic field lines. ~Do they point toward or away from the North magnetic
pole?
Do the magnetic field
lines point toward or away from south magnetic pole?
Part II: ~Magnetic field around current-carrying wires
http://www.magnet.fsu.edu/education/tutorials/java/magwire/index.html
Click on the link above.
Notice that the arrow indicating the direction of current is OPPOSITE the
direction the electrons are flowing. ~For some reason that nobody really
understands, we define current as a flow of positive charges, which is opposite
the direction of the flow of electrons. ~Weird, but true. Sketch the
direction of the magnetic field produced by this wire. (Use an x to
represent a field going into your paper and an o to represent a field coming
out of the paper.)
http://physicsed.buffalostate.edu/SeatExpts/resource/rhr/rhr.htm
Click on the link above.
Scroll down to right-hand rule #2. Explain the right-hand rule for
determining a magnetic field around a wire. ~Label the diagram on your
worksheet. ~What value does your thumb represent? What value do your
fingers represent?
Draw the electric field
around the following wires (shown on your paper). Remember that an x is
an arrow pointing into the page and an o is an arrow pointing out of the page.
As we know, magnets can
either repel or attract one another. Which means that
so can current-carrying wires (since they are magnets!).
Watch the video below.
http://www.youtube.com/watch?v=43AeuDvWc0k
When the wires are connected in parallel (switch pulled backward,
the circuit is shown below. The magnetic fields around the wire are as
shown on your paper:
Do the wires attract or repel when they are connected in parallel?
Try to explain why, using the magnetic fields above. (Hint:
do north poles attract other north poles, or do they attract south
poles?)
When the wires are connected in parallel (switch pulled backward,
the circuit is shown on your paper. Sketch the magnetic field around the
two vertical wires:
Do the wires attract or repel when they are connected in series?
Try to explain why. (Just do your best – this is a difficult
question)
Part III: ~Charges
moving through magnetic fields
http://www.curriki.org/nroc/Introductory_Physics_2/lesson38/Container.html
Describe the right-hand rule for charges moving through magnetic
fields. What does your thumb represent? What does your pointer
finger represent? What does your middle finger represent?
Is the right-hand rule used for positive or negative charges?
What path does a charged
particle take when it is moving through a magnetic field?
http://www.regentsprep.org/Regents/physics/phys03/cdeflecte/default.htm
Click on the above link and
watch the animation. Using your Right-hand rule, predict the direction of the
force on a particle traveling through the magnetic field shown (the field is
into the page). Is this the same direction as the force shown? If
not, why not?
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o
X x x x o o o o