Light and Electricity Activities: Divisions III and IV

Activity 1: Construct a Galvanometer

Integration Notes:
This is the first in a series of four activities designed to build skills toward the Phase 2 challenge to construct a generator, according to the requirements of Dr. Dave Irvine-Halliday's Nepal Light Project.

In order to give students a sense of purpose, we suggest spending some time reviewing the online description of the Nepal Light Project and the background material on the concepts behind the project.

For electronic resources and ideas for online interaction with the Everest team, review the Implementation and Integration Notes for Energy and the Environment, Phase 1 - Divisions III and IV.

Learner Outcomes:
Students will:

• Understand that a current-carrying wire will create a magnetic field, and
• Demonstrate their understanding of this creation of a magnetic field by constructing a galvanometer.

Materials: for each student or small group of students building a galvanometer

• cardboard
• compass (students may construct their own compass, following instructions in the Div I Activities)
• 2 meters (approximately) of insulated wire
• D-cell battery
• tape, scissors, ruler, pencil, etc

Introduction/Purpose:
Students will construct a galvanometer to indicate the presence of a current. The galvanometer will consist of a compass within a small box that is wrapped with insulated wire. This is the first step in gaining skills to complete the challenge in Phase 2.

Procedure:

1. Students must first see that a current-carrying wire will deflect the needle on a compass. To demonstrate this, ask students to connect one end of a short length of wire to the positive terminal of a D-cell battery and the other end to the negative terminal. Ask them to try to make the compass needle turn around by waving the wire near the compass.

Caution: The short wire may get hot if connected to the battery for an extended period of time.

2. Have them experiment with switching the positive and negative terminals and then repeating the activity and comparing the results with what they witnessed in step 1.

3. Ask the students what would happen if they used a smaller battery (the deflection of the compass needle would be smaller and less noticeable). Ask them how they could amplify the effect of the current-carrying wire on a compass needle. (lead them to the idea that holding more current-carrying wire above the compass will amplify the effect)

4. Get the students to design a current detector, or galvanometer, using the materials that you provide. Encourage the students to think through a design before they start construction. The steps that follow outline one possible way of making a galvanometer.

a) First you must make a container that will hold the compass and allow the wire to be wrapped around it. To do this, first set the compass on a piece of cardboard and trace around the compass.

b) Remove the compass from the cardboard and construct a small box around the tracing of the compass with about 1 cm of space between the compass and the sides of the box.

c) Tape the compass to the inside bottom of the box, within the tracing that was done in step "a," so that it does not move around indide the box.

d) Tape the wire to the box, but leave approximately 25 - 30 cm of wire loose so that it can be attached to the generator.

e) Wrap the wire around the top and bottom of the box so that you can still see through the gaps in the loops of wire to check for the deflection of the compass. Make sure that it is wound around the cardboard 10 - 15 times.

f) Test your galvanometer by attaching a D-cell battery to the two wire terminals and observe the result on the galvanometer.

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Activity 2: Calibrate the Galvanometer

Integration Notes:
This is the second activity in a series of four activities designed to build skills towards the Phase 2 challenge to construct a generator, according to the requirements of Dr. Dave Irvine-Halliday's Nepal Light Project.

In order to give students a sense of purpose, we suggest spending some time reviewing the online description of the Nepal Light Project and the background material on the concepts behind the project.

For electronic resources and ideas for online interaction with the Everest team, review the Implementation and Integration Notes for Energy and the Environment, Phase 1 - Divisions III and IV.

Learner Outcomes:
Students will:

• Employ the use of resistors when calibrating their galvanometer.
• Understand and be able to state the purpose of a resistor in a circuit.

Materials: for each group of students

• Galvanometer constructed in activity 1
• 1 D-cell battery
• a variety of resistors
• 15 to 20 cm piece of wire
• pencil, tape, etc
• two or three different radio resistors

Procedure:

1. Attach one of the wires leading from galvanometer you made in the first activity to either the positive or negative terminal of the D-cell battery. Use tape to fasten the end of the wire to the battery.

2. Attach the 15 to 20 cm long piece of wire to the other terminal of the battery. Use tape to make sure that it is securely fastened to the terminal.

3. Touch the free end of the wire coming from the galvanometer to the short wire that you have just attached to the battery. The compass needle in the galvanometer will move or deflect. Record the amount of deflection on a data chart, along the lines of the one described below. What is the maximum deflection of the compass needle? (A: 90 degrees, or a quarter turn)

Your chart should have three headings across the top: Amount of Resistance (can simply count the number of "bands" on the resistor itself); Drawing showing the deflection of compass needle; Actual number of degrees of deflection.

Below, start with "Zero - no resistors added," under the first heading and fill in the chart according to the experiment results.

4. Begin experimenting with adding different sizes of resistors to the circuit. Insert the resistors in your circuit by attaching one side of them to the free end of the wire coming from the galvanometer and the other side to the short length of wire that you attached to the battery.

Calibrating Note:
Experimenting with different resistors in order to reduce the amount of deflection of the compass needle will come in handy in the following activities. Students will be asked to compare what factors affect the amount of current generated by a device and will be asked to use the galvanometer to measure the amount of current produced. The resistors in this activity will provide the practice students need in order accurately measure the amount of current generated.

Back to: Light and Electricity Activities: Division III and IV

Activity 3: Make a Generator

Integration Notes:
This is the third activity in a series of four activities designed to build skills towards the Phase II challenge to construct a generator according to the requirements of Dr. Dave Irvine-Halliday's Nepal Light Project.

In order to give students a sense of purpose, we suggest spending some time reviewing the online description of the Nepal Light Project and the background material on the concepts behind the project.

For electronic resources and ideas for online interaction with the Everest team, review the Implementation and Integration Notes for Energy and the Environment, Phase 1 - Divisions III and IV.

Learner Outcomes:
Students will:

• Construct a generator.
• Demonstrate understanding of how a magnetic field can induce a current in a wire.

• toilet paper roll
• 5 meters of insulated wire
• bar magnet
• tape, scissors, ruler, pencils, etc
• Galvanometer from activity # 1

Procedure:
1. Leaving approximately 20-30 cm of wire free on one end, wrap the wire around the paper roll in a tight, even pattern. Leave approximately the same amount of wire free on this other end of the generator.

2. Attach the free ends of the wire to the ends of the wires from the galvanometer.

3. Have one student hold the paper roll while another student moves the magnet.

4. The student who is holding the magnet must quickly move the magnet inside the paper roll. If the paper roll is fastened to a desk the bar magnet can be slid in and out of the paper roll.

5. Observe the effect of the movement of the magnet on the galvanometer and record.

Back to: Light and Electricity Activities: Division III and IV

Activity 4: Variables affecting the generation of current

Integration Notes:
This is the fourth activity in a series of four activities designed to build skills towards the Phase 2 challenge to construct a generator according to the requirements of Dr. Dave Irvine-Halliday's Nepal Light Project.

In order to give students a sense of purpose, we suggest spending some time reviewing the online description of the Nepal Light Project and the background material on the concepts behind the project.

For electronic resources and ideas for online interaction with the Everest team, review the Implementation and Integration Notes for Energy and the Environment, Phase 1 - Divisions III and IV.

Learner Outcome:
Students will discover factors that affect the strength of the current generated in a hand generator.

Materials:

• Hand generator made in Activity 3
• Galvanometer made in Activity 1

Introduction/Purpose:
As students participate in this activity, they will determine which variables affect the amount of current generated by the generator constructed in Activity 3. Students will describe how each of the variables affect their generator.

Procedure:
1. Ask the students to describe which factors they think will affect the amount of current generated by their generator. Lead them to a list that includes the variables below. Each variable listed below also includes suggestions on how to test the effect of that variable on the amount of current generated.

1.a) Number of coils of wire
Count the number of coils of wire used to wrap the generator. Begin with a relatively small number of coils, check the current generated and then increase the number of coils by 5 or ten wraps. Measure and record the amount of current generated for each trial.

1.b) Speed of the magnet within the coil
Have one student move the magnet within the coil at a fairly slow but constant rate. Another student can time the number of passes the magnet makes within the coil of wire in ten seconds while another student measures the amount of current generated. Record the amount of current and then have the student who is moving the magnet increase the speed of the magnet and repeat the process.

Graphing the data will show a relationship between the speed of the magnet and the current generated.

1.c) Circumference of the coil of wire
Cut the toilet paper roll lengthwise. This will allow students to change the diameter of the coil of wire by overlapping the toilet paper roll. Students could try four or five different diameters and check the resulting current.

2. Recalibrate your galvanometer to compensate for the smaller amount of current that will be generated in these experiments before you test how the factors listed above affect the amount of current generated.

NOTE: Students must control all other variables when testing a single variable to be sure that the observed result is attributable only to the manipulated variable.

For example, when testing how the circumference of the coil of wire affects the amount of current generated, students must be careful to make sure that they keep the speed of the magnet constant for all of the trials for each diameter.

They must also make sure that they are using the same amount of wire wrapped around the toilet paper roll for each trial, so that they are only changing the diameter of the coil and not the amount of wire that is wrapped around the toilet paper roll.

Back to: Light and Electricity Activities: Division III and IV