Earth and Environmental Science 11–12 · Year 12
Output of a solar cell against light intensity and angle
Module 8: Resource Management
The idea
A photovoltaic cell’s short-circuit current follows the light it intercepts, so tilt, shading and time of day set the yield of a renewable energy resource.
What you need
- a small solar cell (about 2 V, 100 mA), a multimeter on a milliamp range to read the short-circuit current directly, and a 10 Ω load resistor with a second multimeter for the contrasting power reading
- lamp on a stand, metre rule, protractor mount, sheets of tracing paper as shading
How to do it
- Connect the multimeter across the cell on a milliamp range so that it reads the short-circuit current, the quantity that is proportional to the light the cell intercepts.
- Move the lamp from 20 cm to 100 cm in steps and record the short-circuit current at each distance; plot it against 1/distance².
- At a fixed distance tilt the cell from 0 to 75 degrees in 15 degree steps and record the short-circuit current; compare with cos(angle).
- Add tracing-paper layers to model cloud and record the fall in short-circuit current.
- Repeat one tilt series with the 10 Ω resistor across the cell, reading voltage and current so that power P = V I, and compare the two shapes: across a load this small the voltage rises with the current, so the power follows the square of the light rather than its cosine.
- Estimate the daily light a fixed panel intercepts against one that follows the Sun, applying the cosine law to the intercepted light rather than to the power across a fixed load.
What you should see
The short-circuit current falls with the square of the lamp distance and with the cosine of the tilt: 0.87 of the perpendicular value at 30 degrees and 0.50 at 60 degrees (cos 30° = 0.866, cos 60° = 0.500), and each paper layer removes a repeatable fraction. Power measured across the fixed 10 Ω load does not follow that law: the cell then works near short circuit, where the voltage across the load rises with the current, so the power follows the square of the intercepted light and falls to about a quarter of its perpendicular value at 60 degrees (0.500² = 0.250). The learner reports the angle at which the intercepted light halves, which quantity follows the cosine law, and the fixed tilt that best matches the site’s latitude.
What changes
- What you change
- lamp distance, tilt angle, or number of shading layers
- What you measure
- short-circuit current (mA), with the power across the fixed 10 Ω load as the contrast
- What you keep the same
- lamp power
- same meter and current range
- ambient light excluded
- cell temperature
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Solar panels need heat, not light.
- A panel gives full output at any angle.
Safety card
Hazards
- hot lamp
Controls
- lamp on a stand
Note
No hazardous chemicals or heat sources: record the activity in the school's RiskAssess risk assessment, following the NSW Department of Education Science safety and compliance page; the Chemical Safety in Schools package is not triggered.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-15EES11/12-5EES11/12-6EES11/12-7
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-11-02
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.