Quick answer: Energy resources are non-renewable (coal, oil, natural gas, uranium) or renewable (solar, wind, hydro, tidal, geothermal, biomass). This grade 8 science lab on energy resources gives the aim, the equipment, the safety points, a step-by-step method, sample results and 8 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
How much does the angle of a solar cell matter? In this lab you tilt a small solar cell away from a lamp, measure the voltage across a fixed resistor, calculate the power and decide how a real roof panel should be placed.
Level: Grade 8 science (Year 9 · Class 8) · Curriculum: MS-ESS3-3
Aim
To investigate how the angle between a solar cell and a lamp changes the electrical power produced.
Equipment
- Small solar cell on a hinged stand
- LED desk lamp
- 20 Ω resistor
- Digital voltmeter
- Protractor, ruler and connecting leads
Safety
Keep water away from the electrical equipment. Do not look directly into the bright lamp. Use only the low-voltage cell and a lamp that has been checked, and switch off when changing the circuit.
Method
- Connect the solar cell, the 20 Ω resistor and the voltmeter across the resistor.
- Place the lamp 30 cm from the cell so that the cell faces the lamp directly. Call this angle θ = 0°.
- Darken the room, switch on the lamp and read the voltage.
- Tilt the cell away from the lamp by 20°, keeping the distance the same, and read the voltage again.
- Repeat for 40°, 60°, 70° and 80°.
Results
Sample measurements from a school lab. The power in the resistor is calculated from V² ÷ R.
| Angle θ (°) | Voltage V (V) | Power P = V² ÷ 20 (W) | P ÷ P at 0° |
|---|---|---|---|
| 0 | 1.80 | 0.162 | 1.00 |
| 20 | 1.74 | 0.151 | 0.93 |
| 40 | 1.58 | 0.125 | 0.77 |
| 60 | 1.27 | 0.081 | 0.50 |
| 70 | 1.05 | 0.055 | 0.34 |
| 80 | 0.75 | 0.028 | 0.17 |
Analysis questions
Question 1 Check the first power
Show that the power at θ = 0° is 0.162 W.Question 2 Power at 40 degrees
Calculate the power in the resistor at θ = 40° when V = 1.58 V.Question 3 Percentage of the maximum
Calculate the power at 60° as a percentage of the power at 0°.Question 4 Describing the pattern
Describe how the power changes as the angle increases.Question 5 Graph
Describe the graph of power against angle and say what it predicts at 90°.Question 6 Real panels
Explain why solar panels on a roof are tilted towards the Sun.Question 7 Uncertainty
The voltmeter reading is uncertain by ±0.02 V. Calculate the percentage uncertainty in V at 80° and in P.Question 8 Improving the investigation
Suggest two ways to improve the reliability of the results.
