The Effect of Solar Energy on
Light or Electrical Output

Standard VI

Students will understand the source and distribution of energy on Earth and its effects on Earth systems.

Objective 01

Describe the transformation of solar energy into heat and chemical energy on Earth and eventually the radiation of energy to space.

Indicator a

Illustrate the distribution of energy coming from the sun that is reflected, changed into heat, or stored by plants.

Intended Learning Outcomes:

  1. Use Science Process and Thinking Skills
    1. Observe objects, events and patterns and record both qualitative and quantitative information.
    2. Plan and conduct experiments in which students may:
      • Identify a problem.
      • Formulate research questions and hypotheses.
      • Predict results of investigations based upon prior data.
      • Identify variables and describe the relationships between them.
      • Plan procedures to control independent variables.
      • Collect data on the dependent variable(s).
      • Select the appropriate format (e.g., graph, chart, diagram) and use it to summarize the data obtained.
      • Analyze data, check it for accuracy and construct reasonable conclusions.
      • Prepare written and oral reports of investigations.

Description of Activity:

Overview

Students will set up a circuit of solar cells connected to an LED light, flashlight bulb, or to a voltmeter. They will place the circuit in full sun, cover cells with a variety of materials (cellophanes, meshes, papers, etc.) and measure or observe the resulting energy changes when solar energy is converted to electricity (measured directly by the voltmeter) or to electricity and then to light (observed in terms of brightness).

Duration of Activity 15 - 45 minutes

Materials:

  • Three or more solar cells*
  • Short lengths of 22 gauge wire (optional, depending on length of leads from cells)*
  • Four to six small alligator clips*
  • One small LED light or flashlight bulb OR one voltmeter capable of measuring voltages below 1.5 volts*
  • Several pieces of cellophane of various colors, of a size sufficient to cover all solar cells when they are wired to form a simple circuit**
  • Screening of different mesh sizes and materials (to cover all cells in a circuit)
  • Wax paper or other translucent material (to cover all cells in a circuit)
  • Glass plate, clear plastic wrap, or other clear material (to cover all cells in a circuit)
  • Sunny room or area in which to place circuit

    * Available from electronic components stores or catalogs.
    **     Available from craft stores or floral shops.

Background Information:

Solar energy can be measured directly (if connected to a voltmeter) or indirectly (by noting light output when cells are wired to a small light bulb). Reducing solar input reduces current voltage, and thereby reduces light output.

Teaching and Learning Strategies:

Prerequisite instruction

  • Students will need to know how to wire a simple circuit:
    • Using alligator clips, attach the three solar cells in series, and attach one lead from the LED light to each end of the solar array.
    • Student will to determine that they need three 0.5 volt solar cells to make a 1.5 volt light work correctly. (Voltages combine by addition.)
  • Students also need to know that we see colors because certain frequencies of light are reflected while all others are absorbed. The atmosphere is transparent to all the frequencies of the visible spectrum. Transparent objects allow light to pass through essentially unimpeded. Translucent objects scatter the light. Opaque objects absorb and reflect light. A leaf appears green because all frequencies of light except those in the green range are absorbed; green light frequencies are reflected.

Invitation to Learn:

Problem:

Determine how many solar cells are needed to make the light work.
Determine what effect various coverings have on the output of solar cells.

Activity

Solar energy can be converted into electricity, and electricity into a wide variety of other energy forms, including light. Using a solar array, students will engage in experiments to determine what happens when they place solar cells in the sun and then manipulate the energy received by the cells with various materials. They will discover changes in energy when solar energy is converted to electricity and/or light.

As students discuss their findings, they should conclude that all frequencies of light allow greater generation of electric energy than a few frequencies. Using materials like wax paper, meshes, etc., they should demonstrate that obstructions reduce the amount of solar energy reaching the cells. The students should relate the above to the amount of energy reaching Earth on sunny verses cloudy, smoky, or hazy days. Students can predict climate changes caused by volcanic eruptions, changing tilt of Earth's axis, pollution, etc. by relating this activity to energy flow in Earth systems.

Safe Operating Procedures

Tell students that as they perform this activity, to be sure all connections are secure. Also, handle all materials carefully to prevent breakage.

Summary of Learning

Assessment

Multiple choice questions

  1. Limiting the frequencies of light on a solar cell
    1. Reduces the amount of electricity produced
    2. Increases the amount of electricity produced
    3. Does not have much effect on the amount of electricity produced
  2. Changing the number of cells in the solar array
    1. Changes the voltage output
    2. Changes the electrical output
    3. Makes no difference in the output
    4. Both (A) and (B) are correct

Extensions

  • Students may be interested in wiring additional cells and/or lights into their array, and experimenting with output in parallel verses series circuits.
  • Some students may also want to investigate using different combinations of colors of substances, or to experiment varying the distance the obstructive materials are placed from the cells.