Contributed by: Council of Chief State School Officers (CCSSO)
Item Description: Students may be in groups for this portion
of the event. After each trial, record your observations in the
data table. Before each of the following trials, separate the magnet
and the galvanometer by several meters and orient the compass so
its needle points due North.
Trials 1-3 |
Requires placing the north end of the magnet inside
the tube. |
Trial 1 |
Hold the magnet still with the tip just inside
the tube. |
Trial 2 |
Move the magnet slowly toward the tube; when the
tip of the magnet is just inside the tube, stop. Then move the
magnet slowly away from the tube and, when the magnet is two
meters away from the tube, stop. |
Trial 3 |
Move the magnet rapidly toward the tube; when
the tip of the magnet is just inside the tube, stop. Then move
the magnet rapidly away from the tube and, when the magnet is
two meters away from the tube, stop. |
Trials 4-6 |
Requires placing the south end of the magnet inside
the same end of the tube as before. |
Trial 4 |
Hold the magnet still with the tip just inside
the tube. |
Trial 5 |
Move the magnet slowly toward the tube; when the
tip of the magnet is just inside the tube, stop. Then move the
magnet away from the tube and stop, as in trial 2. |
Trial 3 |
Move the magnet rapidly toward the tube; when
the tip of the magnet is just inside the tube, stop. Then move
the magnet rapidly away from the tube and stop, as in trial
2. |
Students were asked the following question: Based on your results,
describe the relationships between: (a) how fast you moved the magnet
and the amount of current that flowed in the wire; and (b) the pole
of the magnet (north or south) that was inside the tube and the
direction of the compass' deflection.
Content Definition: When a coil of wire crosses a magnetic
field it creates a current. The direction and strength of the current
is indicated on the galvanometer. When the movement of the magnet
is reversed the current is reversed. When the south pole of the
magnet is inserted in the opposite end of the coil, the current
is reversed. To increase the strength of the current, increase the
movement of the magnet and/or increase the number of turns in the
coil. The current can also be increased by using a stronger magnetic
force. Electric current is generated by the movement of the coil
in the magnetic field or the movement of the magnet in the coil.
When both the coil and the magnet are stationary, no current is
produced.
Mechanical energy, in the form of the hand moving the magnet into
and out of the wire-wrapped tube, caused the magnet to cross the
magnetic lines which creates a current.
Data Table
Trial |
Pole of magnet inside tube (N or S) |
Motion of magnet relative to tube (none,
slow, fast) |
Amount of deflection (degrees) as magnet moves: |
Direction of deflection (E for east of north; W
for west of north) as magnet moves: |
toward tube |
away from tube |
toward
tube |
away
from tube |
1 |
N
|
none
|
0-2 degrees
|
0-2 degrees |
W
|
|
2 |
N
|
slow
|
0-5 degrees
|
0-5 degrees |
W
|
E
|
3 |
N
|
fast
|
about 10 degrees
|
about 10 degrees |
W
|
E
|
4 |
S
|
none
|
0-2 degrees
|
0-2 degrees |
E
|
|
5 |
S
|
slow
|
0-5 degrees
|
0-5 degrees |
E
|
W
|
6 |
S
|
fast
|
about 10 degrees
|
about 10 degrees |
E
|
W
|
NOTE: Three important concepts in this exercise are:
- The amount of deflection is positively correlated to
the speed of the magnet as it moves forward and away from the
coil.
- The direction of deflection is changed by:
- Changing the pole of the magnet induced into the coil.
- The direction the magnet is moving, either toward or away
from the coil.
Scoring Parameters:
- Based on data collected, the speed of the magnet's motion positively
corresponds to the strength of the current (i.e., faster speed,
more current).
- Based on data collected, changing the magnetic pole inserted
into the coil reversed the direction of deflection.
Score Level Descriptions:
NS |
Blank or irrelevant response is given. |
1 |
Student response indicates minimal knowledge of the generation
of electricity using a coil of wire and a magnetic field. Response
says something about the magnet, current, and/or deflection
of the compass.
- We put the north pole in and out of the tube six times.
|
2 |
Student response indicates some knowledge of the generation
of electricity using a coil of wire and a magnetic field. The
student discusses variation in speed of the magnet OR
inserting the north or south pole of the magnet into the coil,
however does not make connections between these aspects of the
event and current generated and/or compass deflection.
|
3 |
Student response indicates an adequate understanding of the
generation of electricity using a coil of wire and a magnetic
field. The student communicates EITHER a positive
relationship between speed of magnet movement and increase
in current OR a change in pole used will reverse
the direction the current is traveling.
|
4 |
Student response indicates a full understanding of the generation
of current and its direction using a coil of wire and a magnet.
Student communicates BOTH a positive relationship between
speed of magnet movement and increase in current AND
the change in the pole will reverse the direction the current
is traveling. |
Item Description: You live along a moving river, and
you have lots of wire, a paddle wheel, and a huge bar magnet. Describe
how you could use these materials to produce an electrical current.
Include a diagram of your setup in your description.
Content Definition: When a coil of wire crosses a magnetic
field it creates a current. Electrical current is generated by the
movement of the coil in the magnetic field or the movement of the
magnet in the coil. Mechanical energy, in the form of the moving
water, can cause either the coil to cross the magnetic field to
create a current.
Scoring Parameters:
- The student applies the materials given in the item (magnet,
wire, and paddle wheel) to construct a generator.
- The student description uses mechanical energy from the river
to move either the magnet or the coil of wire (in relation to
a corresponding coil or magnet) to produce electricity.
- The student provides a diagram corresponding to the description.
Score Level Descriptions:
NS |
Blank or irrelevant response is given. |
1 |
The student response indicates a minimal understanding of
the use of the materials to construct a generator. The response
offers at least one strategy but is unable to relate it to the
production of an electrical current. The diagram lacks one or
more key components of a generator.
- I'd use the paddle wheel on the river and get an electrical
current.
- I'd get energy from the water to make electricity.
|
2 |
The student response indicates some understanding of the use
of the materials to construct a generator. The response uses
or mentions each of the materials from the prompt but has an
incomplete relationship between the materials and the production
of an electrical current. The diagram is adequate but not
complete.
- The paddle wheel turns in the water and the magnet has
wire around it.
|
3 |
The student response indicates an adequate understanding applying
the materials to construct a generator. The response describes
how to use the materials to produce a current however one step
in the process may be missing to make the model functional.
The diagram is complete and accurate according to the description.
- The moving magnet within the coil of wire makes an electrical
current.
|
4 |
The student response indicates a full understanding of the
use of the materials to construct a generator. A full description
includes a thorough and accurate discussion of how each material
functions to make the working generator. A complete diagram
is included.
- The paddle wheel turns the mechanical energy of moving
water into electrical energy by moving the magnet within
a coil of wire around the paddle wheel. When the coil of
wire crosses the magnetic field, a current is created.
|
|