Solar Power
Grades 6-8
Concept:
In an electrical circuit, the measure of power (watts) is the result of
multiplying volts x amps.
Objective: Students will:
• connect solar cells in series and parallel, will measure volts and amps, and
will calculate watts.
OR - State Standards:
ENERGY
Understand energy, its transformations, and interactions with matter.
Describe and explain various energy transfers and resulting
transformations.
Trace the flow of energy transformations in a system
Time:
2 40-minute periods
Materials:
Solar Cells (Please take extra care with the cells – they break easily.)
Alligator Clips
Multi-Meter
Light source
Solar Power
Procedure:
1. To learn the use of the Multimeter you should measure and record the
volts and amperes (amps) generated by each of the cells you are going to use.
Note: If this experiment is to continue for more than one day be sure that you
use the same solar cells each day.
Attach an alligator clip to each of the two silver leads on the underside of a
solar cell. Be careful not to damage the leads by pulling or twisting them.
2. Assemble the Multimeter by inserting the circular end of the red cord in
the middle hole on the lower right of the meter face and the circular end of
the black cord in the bottom hole.
3. Clip the left alligator clip from the solar cell to the red cord probe and the
right alligator clip to the black cord probe on the Multimeter. You will note
that the display in the center of the Multimeter has a movable dial in the
center. Look carefully at the dial and you will see a small indentation on one
end of the dial. This is the pointer end!!
Start you measurement by adjusting the pointer end to DCV 20. Switch the
Multimeter on with the ON/OFF switch.
Note: Get in the habit of turning this switch off if you are not measuring.
4. Record the value shown in the volts section of the chart provided. Rotate
the pointer end to DCA 20m and record the value shown in the amps section
of the chart. Do this for each of the cells you are using. Do the math
indicated and you should find that the watts developed by each cell are close
to being equal.
5. Using the alligator clips link
two cells together as shown in
Figure 1. Measure and record
both the volts and the amps.
Continue linking and measuring
until all four cells are connected
in a series circuit.
Fig. 1
6. Again using the alligator
clips link two cells together as
shown in Figure 2. Measure
and record the volts and amps.
Continue linking and
measuring until all four cells
are connected in a parallel
circuit.
Fig. 2
7. Again using the alligator clips link two cells together as shown in Figure
3. Measure and record the volts and amps.
Figure 3
8. You now have data that can lead you to conclusions about some basic
differences between series and parallel circuits. Start by doing the math. In
each row of your chart you can see that volts X amps = watts. When you
have finished the calculations use the blank graph to first represent watts vs.
the number of cells for the series circuit and then the same for the parallel
circuit.
Are the lines created by graphing watts similar or different?
Are the volt and amp values used to calculate watts the same for both the
series and parallel circuits? Explain!!
For each of the configurations (Figs. 1, 2, 3) you should expose the solar cells
to a uniform light source and measure the volt and amp readings with a
Multimeter. Attach the Multimeter to the appropriate (+) and (–) terminals of
each configuration.
[TEACHERS: THE MULTIMETERS ARE TO BE USED TO TEST THE SOLAR
CELLS AND BATTERIES, NOT AC OR DC LINE VOLTAGES, CURRENTS, OR
RESISTANCES.]
Students: set the Multimeter at DCV = 20 to measure volts and at DCA = 20
to record amps.
To figure watts enter volts and amps into the following formula:
_____volts X _____amps = _____watts
Record the volts, amps, and watts in the following chart:
Fig 4
•
•
•
What is the relationship between a series connection and volts, amp,
and watts
What is the relationship between a parallel connection and volt,
amps, and watts?
What is the relationship between the combination connection and
volt, amps, and watts?
Which combination would be best to run a:
1.5-watt bulb, ipod, etc.