Science and Technology K–6 · Year 6

Designing a light for a blackout

Science understanding: Physical sciences

PracticalLow risk

The idea

Electrical energy from cells is transformed into light in a circuit, and a designed light with a switch, a chosen light source and a reflector meets a need only when it is tested against measured criteria.

What you need

2 AA 1.5 V alkaline cells in a holder
a 2.5 V 0.3 A torch globe in a holder, and a white LED module with a built-in resistor (current rating on the packet); a white LED needs about 3 V before it conducts, so a module sold for 3 V has almost nothing left across its resistor on two cells, and a 3-cell holder (4.5 V) should be on hand for it
insulated wire, and a push switch or a paper-clip-and-split-pin switch
a digital multimeter
a light meter or a tablet light-meter app
recycled containers, card, tape and aluminium foil for a reflector
a stopwatch

How to do it

Define the need with the class: a light to read a book by during a blackout. Agree measurable criteria: a light level on a page 30 cm away, a switch that works every time, at least 30 minutes of running, and mostly recycled materials.
Set the light-level target: measure the reading on a page 30 cm from a room light that everyone can read by comfortably.
Draw a labelled design with a circuit diagram using standard symbols.
Build the light. Measure the current from the cells with the globe, then with the LED module.
Test: light level on the page at 30 cm with and without the foil reflector; switch operated 20 times; run for 30 minutes and measure the cell voltage while the light is on at the start and at the end.
Evaluate the design against each criterion, change one thing and retest.
Write a product report for another class that states each criterion beside its measured result.

What you should see

Both light sources work only in a complete circuit and go out every time the switch opens. The globe draws about 0.35 A from 2 fresh AA cells, about 1.0 W; the LED module's current is the measured one, not the packet rating: on two cells (about 3.1 V fresh, about 2.9 V under load) a module rated at 20 mA has little voltage left across its built-in resistor, so it draws less than its rating and dims as the cells fall, while on the 3-cell holder it reaches the rating. At a measured 20 mA it takes 0.02 A and about 0.06 W, one seventeenth of the globe's power, so it runs the same cells down far more slowly; divide your own two measured currents for the ratio your light gives, and record which supply the 30-minute run used. A foil reflector behind either source raises the reading on the page at 30 cm. After 30 minutes the cell voltage under load has fallen more in the globe version than in the LED version. A design meets the brief when every agreed criterion has a measured value beside it; one that fails a criterion is modified and retested, which is the design process the task assesses.

What changes

What you change: light source (globe or LED) and reflector (with or without)
What you measure: light level on the page at 30 cm, current drawn, cell voltage after 30 minutes
What you keep the same: same type of cell
30 cm distance
same light meter
same room lighting (lights off)

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A brighter light always uses the same energy as a dimmer one.
A switch makes electricity; it only opens or closes the path.
A design is finished once it works the first time (it is finished when it meets measured criteria).

Safety card

Low riskLearners carry it out

Hazards

a short circuit heats the cells and wires
the globe gets hot
sharp edges on cut containers

Controls

switch and circuit checked by the teacher before the cells go in
globes cooled before handling
scissors only, no craft knives
1.5 V cells only; never mains

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST3-8PW-ST ST3-2DP-T
Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST3-DDT-01 ST3-CWT-01
Australian Curriculum v9AC9S6U03AC9S6H02AC9S6I02AC9S6I06

Sources

The pages the author read to write this activity.

All Concept Studio activities