Principles of the Physical World: Senior Cycle Physics · 5th Year

Active learning ideas

Tiny Switches in Our Devices

Active learning works for this topic because transistors are abstract components that become concrete when students build and manipulate them. Hands-on work with circuits and simulations helps students move beyond memorizing terms to seeing how small inputs control larger outputs in real time.

• NCCA Curriculum Specifications
• NCCA: Primary Curriculum - Science - Energy and Forces

• 20–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• 45 min · Small Groups

Circuit Building: Basic Transistor Switch

Supply breadboards, NPN transistors, 1kΩ resistors, LEDs, and 9V batteries. Students connect the transistor base to a push-button switch via resistor, collector to LED anode, and emitter to ground. Test the circuit: press button to light LED, observe no light when released. Discuss current amplification.

How does a remote control turn on a TV?

Facilitation Tip

During Circuit Building, circulate with a multimeter to check students’ transistor base connections before they power up, ensuring proper current flow paths.

What to look for

Present students with a diagram of a simple transistor switch circuit. Ask them to label the input signal and the output current path, and describe what happens to the output when the input is 'on' and 'off'.

Activity 02

• 30 min · Pairs

Simulation Pairs: Logic Gate with Transistors

Use Tinkercad or Falstad simulator. Pairs build a NOT gate: input to transistor base, output from collector to LED. Toggle input high/low, record output states. Extend to AND gate by wiring two transistors in series.

What makes a phone screen light up when you touch it?

Facilitation Tip

For Simulation Pairs, pair students with different logic gates to compare their transistor arrangements, fostering discussion about why NAND and NOR require more components.

What to look for

On a slip of paper, have students answer: 'In your own words, explain how a transistor acts like a light switch for electricity. Give one example of a device where this is important.'

Activity 03

• 25 min · Pairs

Teardown Exploration: Device Internals

Provide old remotes or calculators for safe disassembly. Students identify integrated circuits housing transistors, sketch layouts, and note switch-like components. Compare to circuit diagrams, hypothesize functions.

How do computers know what to do?

Facilitation Tip

In Teardown Exploration, assign small groups specific devices to trace current paths through transistors, using magnifying lenses to spot the tiny semiconductor regions.

What to look for

Pose the question: 'How does the ability of transistors to switch on and off millions of times per second enable the complex functions we see in modern smartphones?' Facilitate a brief class discussion, guiding students to connect speed to functionality.

Activity 04

• 20 min · Whole Class

Whole Class Demo: Touch Sensor Model

Demonstrate capacitive touch with foil, transistor, and buzzer. Class predicts outcomes as capacitance changes with hand proximity. Measure gate voltage shifts, link to phone screens.

How does a remote control turn on a TV?

Facilitation Tip

During the Whole Class Demo, pause after the touch sensor model to ask students to predict what happens when they move their finger closer or farther from the foil sensor.

What to look for

Present students with a diagram of a simple transistor switch circuit. Ask them to label the input signal and the output current path, and describe what happens to the output when the input is 'on' and 'off'.

A few notes on teaching this unit

Approach this topic by starting with simple switch circuits before moving to logic gates, as research shows students need to master single-transistor behavior before scaling to complex systems. Avoid analogies that compare transistors to human thinking, since this reinforces misconceptions about digital precision. Instead, use measurements and diagrams to anchor understanding in observable phenomena.

Successful learning looks like students explaining how transistor switching enables digital logic, accurately labeling current paths in circuit diagrams, and connecting device functions to the microscopic behavior of semiconductors. Expect clear on/off behavior in circuits and confident descriptions of binary states.

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Watch Out for These Misconceptions

• During Circuit Building: Basic Transistor Switch, watch for students describing transistors only as amplifiers rather than switches.

  Pause their work to measure base and collector voltages, then ask them to note how a small base current fully turns the LED on or off. Have them sketch the two distinct states in their notebooks.

• During Simulation Pairs: Logic Gate with Transistors, listen for students saying touchscreens work by pressing buttons.

  Ask them to adjust the finger capacitance value in the simulation and observe how the transistor threshold changes. Have them relate this to the foil sensor in the Whole Class Demo to correct the mechanical pressure idea.

• During Whole Class Demo: Touch Sensor Model, expect some students to think computers process information like brains.

  After the demo, show a logic gate simulation running millions of cycles per second and ask students to explain how simple on/off operations create complex outputs like app icons or text.