◈ SCIENCE LABCLASSROOM INVESTIGATION / PHYSICSTeacher guide ↗
← Experiment libraryGRADES 9–12 · 35–50 MINUTES
DESIGN CHALLENGE / CURRENT, RESISTANCE & POWER

Build a reliable warning circuit.

A model circuit must operate within two limits. Can your evidence justify a design?

Start with the design brief.

01 / THE PROBLEM

A signal that can be trusted.

A school is evaluating a battery-powered warning module. Your team is testing its electrical supply with a resistor as a dummy load. Too little current could fail to operate the module; too much power would exceed this test load’s rating.

Your job: recommend a supply voltage and nominal load resistance, supported by repeated measurements and calculations.

OPERATING CURRENT35–55 mA
LOAD POWER LIMIT≤ 0.250 W

These are specifications for this fictional test module. The resistor represents a test load, not a real LED, buzzer, or complete warning device.

What you will learn

  • Design a controlled comparison and use repeat measurements.
  • Measure current in series and voltage in parallel.
  • Use I = V/R and P = VI to analyze a design.
  • Evaluate measurement variation, component tolerance, and evidence limits.
THE DESIGN ENVELOPE

Available parts

1–12 V DC supply settings, in 1 V steps.
40–200 Ω nominal resistance, in 10 Ω steps.
Ammeter, voltmeter, switch, and leads.

Important limits

We are studying a low-voltage virtual circuit. A real device would also need environmental testing, protection, a suitable power source, and component-specific checks.

Your deliverable

A lab report with a test plan, raw data, calculations, a controlled-comparison graph, and a claim supported by evidence.