The method and the results are on the energy resources lab. Do the analysis yourself first, then check the answers below.
Quick answer: Energy resources are non-renewable (coal, oil, natural gas, uranium) or renewable (solar, wind, hydro, tidal, geothermal, biomass). These answers go with the grade 8 science lab on energy resources: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
These model answers use the sample table. Your own voltages will differ a little, but the power should fall steadily as the cell turns away from the lamp, reaching about half its maximum near 60°.
P = 1.58² ÷ 20 = 2.4964 ÷ 20 = 0.125 W, so the power is 0.125 W.
Question 3 Percentage of the maximum
P at 60° = 1.27² ÷ 20 = 0.0806 W. Percentage = 0.0806 ÷ 0.162 × 100 = 49.8 %, which is about 50 %.
Question 4 Describing the pattern
The power decreases as the angle increases, slowly at first and then faster. Power falls as θ increases.
Question 5 Graph
The graph is a curve that starts at 0.162 W at 0° and falls towards zero as the angle approaches 90°, when the light just skims the cell. The prediction at 90° is close to zero.
Question 6 Real panels
A tilted panel faces the Sun more directly, so more light falls on its surface and the power is higher. It keeps θ small.
Question 7 Uncertainty
Percentage uncertainty in V = 0.02 ÷ 0.75 × 100 = 2.7 %. Because P depends on V², the uncertainty in P is about double, which is about 5.3 %.
Question 8 Improving the investigation
Any two of: repeat each reading and average; shield the cell from other light; keep the lamp distance fixed with a ruler; let the lamp warm up first; use a protractor fixed to the stand. Repeat and shield from stray light are good examples.
