Introduction
to Electromagnetism
Leader:
_____________________________ Recorder:
___________________________
Skeptic:
_____________________________ Encourager: _________________________
Materials
2
x Genecon 2
x Alligator patch cords (light weight)
Small
coil with iron rod Wood
block with two screw eyes
Compass Stiff
wire bent in shape of U
Masking
tape Horseshoe
Magnet
Ring
stand with clamp
Introduction
In this activity we will explore some of
the basic ideas of electromagnetism.
Electromagnetism refers to the magnetic field produced by an electric
current.
Procedure
The Magnetic Field of a Solenoid
Begin by plugging the Genecon cable into
the Genecon. Connect the alligator clips
on the Genecon cable to the connectors on the small solenoid. Place the solenoid on the table with the bore
oriented horizontally. Place the small
iron rod so that it is a little more than halfway into the bore of the
solenoid.
Q1) Turn the crank of the Genecon one time
rapidly while observing the iron rod.
Record what happens to the iron rod.
(If nothing happens notify your instructor to assist you.)
Q2) Repeat the procedure only this time turn the
crank of the Genecon in the opposite direction.
Record what happens to the iron rod.
Q3) Reverse the orientation of the rod and
repeat. Record what happens.
Q4) Turn the Genecon in the opposite direction
and repeat. Record what happens to the
rod.
Q5) Is the iron rod always attracted into the
coil.
Q6) Keeping in mind that the iron rod is a
temporary magnet, suggest an explanation for what is happening to the iron rod
when you turn the crank.
Q7) Is the rod attracted into the center of the
coil before you turn the crank of the Genecon or only when you turn the crank?
Q8) When you turn the crank of the Genecon is
their a current in the coil?
Q9) When a current flows in the coil is a
magnetic filed produced?
Q10) A common application of an iron rod inside of
a solenoid is to make a switch to turn on and off and electric circuit. Describe how you could make a switch using an
iron rod and a solenoid.
It appears that when we turn the crank we
produce a magnetic field in the solenoid.
We would like to verify that observation and determine some properties
of the resulting magnetic field. Connect
the alligator clips on the Genecon cord to an alligator clip patch cord. Wrap the patch cord in a line around the
center of the compass so that it makes three
turns around the compass. You may
want to use some tape to secure the cord. Orient the compass so the compass
needle is parallel to the turns of the wire and turn the Genecon handle at a
constant rate. Be careful not to turn the crank handle too fast as this can break the
Genecon.
Q11) What happens to the compass needle when you
turn the crank?
Wrap
the entire patch cord around the
compass and turn the Genecon handle at the same rate as in the previous
question.
Q12) Is it easier to produce the same effect as
you described in question Q11)?
Turn
the crank of the Genecon in the opposite direction.
Q13) Record what happens to the compass needle.
Q14) Did this observation differ from the previous
one in any way?
Orient
the compass so that the compass needle is perpendicular to the coil of wires.
Q15) Turn the crank of the Genecon and record what
happens to the compass needle.
Q16) Turn the crank in the opposite direction and
record what happens to the needle in this case.
Q17) Remembering that the compass needle is a
magnetic dipole and will align with the direction of the magnetic field, what do questions Q11) - Q16) tell you about
the direction that the magnetic field of a solenoid points. Specify the direction in terms of the
orientation of the coils.
Q18) Based on your observations, does the magnetic
field depend on the direction that the current flows in the solenoid? If so, how?
S19) Summarize your observations about the
strength and direction of the magnetic field of a solenoid.
Electromagnets
Wrap the patch cord tightly around the
iron rod with as many turns as you can fit.
Have one person turn the crank while another holds the
electromagnet.
Q20) Hold the electromagnet near the compass while
turning the crank. Does it effect the
compass?
Q21) Try moving the electromagnet around to both
poles of the compass and try both sides of the electromagnet. Does the electromagnet behave like a
permanent or a temporary magnet? Explain
giving your evidence.
Remove
the iron rod from the coil but leave the coil the same. Repeat your procedure with the compass and the
coil without the iron rod.
Q22) Does the electromagnet - without the iron rod
- behave like a permanent or a temporary magnet? Explain giving your evidence.
.
Q23) Does the electromagnet seem to be stronger
with or without the iron rod? Explain.
Q24) Use the fact that the iron rod is a temporary
magnet toexplain why the magnetic field of the electromagnet is stronger when
the iron rod is present.
A Very Simple Motor
Set the U-shaped magnet on the table with
one pole on the table and one pole in the air.
Use the ring stand and the clamp to hold the wood base with two
hooks. Very loosely suspend the U-shaped
wire from the hooks, adjusting the height so that bottom of the wire is halfway
between the poles of the magnet. Make sure that the wire is free to swing on
the hooks.
Turn the crank of the Genecon back and
forth about a quarter turn each way.
Q25) Record what happens to the wire.
Q26) Draw a sketch of this very simple motor. Show the magnetic field on your sketch.
Q27) When current flows on the wire, indicate the
direction of the force on the wire in your sketch.
Stop
the wire and turn the Genecon continuously in one direction.
Q28) Record what happens in this case.
Q29) Why is the result different when you turn the
crank continuously in one direction than when you turn the crank back and
forth?
The Equivalence of a Generator and a Motor
Connect the alligator clips of two
Genecons together. Place one on the
table and turn the crank of the other.
Q30) Describe what happens?
Turn
the crank in the opposite direction.
Q31) Describe what happens. How is it different than previously?
Note
that when you turn the crank of the Genecon, it acts like an electric
generator. The generator converts
mechanical work into electrical energy.
Q32) What process is happening in the second
Genecon?
Q33) How do a generator and a motor seem to be
related?