Contributed by: Council of Chief State School Officers (CCSSO)
Science Education Assessment Project
Description:
Students construct and use a simple galvanometer to detect the presence
of an electric current and to determine the amount of the current.
This task is designed to take students approximately 4050 minutes
to complete.
The activity portion is done in small groups of 4. The followup
questions are completed individually by each student working alone.
Overall Task Content Area:
 Physical Science
Specific Knowledge Areas:
 Motions and Forces
 Energy
Performance Expectations:
 conducting investigations
 using equipment
 gathering, organizing, and representing data
 formulating conclusions from investigational data
 applying scientific principles to develop explanations and
solve new problems
National Science Education Standards:
8 A SI 1: Ability necessary to do scientific inquiry:
Grades 58
1.4 Develop descriptions, explanations, predictions, and models
using evidence. Students should base their explanation on what they
observed, and as they develop cognitive skills, they should be able
to differentiate explanation from description — providing causes for
effects and establishing relationships based on evidence and logical
argument. This standards requires a subject knowledge base so the
students can effectively conduct investigations, because developing
explanations establishes connections between the content of science
and the contexts within which students develop new knowledge.
8 B PS 3: Transfer of energy: Grades 58
3.4 Electrical circuits provide a means of transferring electrical
energy when heat, light, sound, and chemical changes are produced.
4 B PS 3: Light, heat, electricity and magnetism:
Grades K4
3.3 Electricity in circuits can produce light, heat, sound,
and magnetic effects. Electrical circuits require a complete loop
through which an electrical current can pass.
(Use the "hot" link on the PALS home page
to check the full text of related National Science Education Standards,
if desired.)
National Council of Teachers of Mathematics:
AL1: Understand patterns, relations and
functions:
Grades 68 f. represent, analyze, and generalize a variety
of patterns with tables, graphs, words, and, when possible, symbolic
rules
Grades 68 g. relate and compare different forms of representations
for a relationship
MEAS2: Apply appropriate
techniques, tools, and formulas to determine measurements:
Grades 68 k. select and apply techniques
and tools to accurately find length, area, volume, and angle measures
to appropriate levels of precision
PS2: Solve problems that arise in mathematics
and in other contexts:
Grades 68
CNX1: Organize and consolidate their mathematical
thinking through communication:
Grades 68
REP1: Create and use representations to
organize, record, and communicate mathematical ideas:
Grades 68
General Instructions to the Teacher:
This task is designed to take students approximately 4050 minutes
to complete.
Students will be working in groups of 4 for the experiment/activity
part of this exercise.
Students work together for up to 20 minutes. They are instructed
to notify you when finished with the group work, and then to go
on to the individual work beginning with question #1. If students
are still working together 20 minutes after the testing begins,
instruct them to cease their group work and begin individual work.
At this point, they may no longer talk. Whether or not they are
just beginning their individual work, remind students that they
now have about 25 minutes to complete the individual activity.
Students should be ready to work as soon as the period begins.
Group assignments should be made in advance. The materials should
be set out at each lab station, if possible. A central supply area,
if needed, should be easily accessible. All supplies should be clearly
labeled.
Materials:
At this station students should have:
 Compass
 Empty box (bottom only)
 Empty toilet paper tube
 One length of 22 gauge insulated magnet wire marked "Galvanometer"
 One length of 22 gauge insulated magnet wire marked "Generator"
 Strong bar magnet with north pole marked "N"
 tape
Advance Preparation:
 Each student will need two wires one will be for the "generator"
and one will be for the "galvanometer"
 To make these wires cut lengths of 22 gauge insulated
magnet wire (looks like plain copper wire) such that the wires
are sufficiently long to make 50 turns around the box with
30 cm left over.
 Attach alligator clips to both ends of each wire.
 Label one wire "Galvanometer" and one wire "Generator" for
each student.
 Label the North pole "N" on each bar magnet.
 The student will need a "box bottom" that is unassembled. If
boxes are assembled simply cut the side corners of each box so
that sides can be positioned flat to the table.
Content Background:
The simple galvanometer is used to detect the presence of an electric
current and to determine the amount of the current. When a magnet
is moved into or out of the coils of wire that are wrapped around
the tube, the changing magnetic field intensity inside the tube
creates a voltage along the wire. Increasing the rate of change
of the field's intensity (in this case moving the magnet more rapidly
into or out of the magnet) or increasing the number of turns of
wire around the tube will increase the voltage. The voltage inside
the wire causes a current to flow inside the wire, so as the voltage
gets higher, the current gets larger. The current produces a second
magnetic field, some of which occupies the space containing the
compass, so as the current gets larger, the second magnetic field
gets more intense. The second magnetic field causes the compass's
needle to be deflected, so as the second field gets more intense,
the deflection of the needle gets larger. Therefore, when a student
rapidly moves a magnet into or out of the tube, the deflection of
the compass needle should be larger than when the magnet is moved
slowly. Finally, the direction of the compass needle's deflection
depends on which pole of the magnet is pointed toward the tube and
on whether the magnet is moving into or out of the tube.
Safety:
 Be careful.
 Teachers and students should always exercise appropriate safety
precautions and utilize appropriate laboratory safety procedures
and equipment when working on science performance tasks.
 Be sure to keep magnetic sensitive items away from the magnets!
E.g. digital watches and calculators.
Extensions/modifications:
 To expand and target the specific NCTM standard(s) to be measured,
ask the students to use ratios to compare the amount of deflection
of magnet movement.
