What the Simulation Shows
The transformer simulation displays a complete transformer diagram drawn live on a canvas, with two mode buttons at the top and interactive sliders that update everything in real time.
The Two Modes: Clicking Step-Up presets the primary turns to 50 and secondary to 150, and clicking Step-Down reverses this to 150 and 50. The entire diagram responds instantly — coil counts, voltages, and the turns ratio all update together.
The Iron Core: A dark rectangular block sits at the centre of the diagram with animated flux lines running horizontally through it. These lines pulse with the AC signal, visually showing the alternating magnetic field being created in the core by the primary coil and inducing a voltage in the secondary.
The Coils: The primary coil (orange) is wound on the left face of the core, drawn as a series of D-shaped loops curving away from the core. The secondary coil (blue) mirrors this on the right face. The number of visible loops on each coil scales directly with the N₁ and N₂ slider values — in step-up mode you can clearly count fewer orange loops on the left and many more blue loops on the right, and the opposite in step-down mode. This makes the turns ratio immediately visible without reading any numbers.
The Circuits: On the left, an AC source symbol (a circle with a live sine wave animating inside it) feeds the primary coil through orange wires. On the right, the secondary coil connects through blue wires to a light bulb that acts as the load. The bulb glows brighter when output voltage is higher, giving a physical sense of the energy delivered to the load.
Direction Arrows: Small arrowheads on all four wire segments pulse with the AC signal, showing current direction reversing on every half-cycle.
The Stat Cards at the bottom show input voltage (fixed at 230 V), the turns ratio reduced to its simplest form (e.g. 1:3), and the calculated output voltage using Vs/Vp = N₂/N₁. The formula with the live ratio value is also displayed directly on the canvas.
The Two Sliders let students set N₁ and N₂ independently between 10 and 200 turns, watching all values and the coil diagram update as they drag.
Suggested Classroom Activity
Topic: Transformers — step-up, step-down, and the turns ratio equation Level: GCSE Physics (Year 10/11) Duration: 25–30 minutes Group size: Pairs
Starter (5 min)
Show the simulation in step-up mode on the board without explaining it. Ask: “The input is 230 V. Look at the output. What has the transformer done — and what do you think caused it?” Take three or four answers. Then ask students to look at the two coils and count the loops on each side. Establish that the number of turns is the key.
Guided Investigation (15 min)
Give students this structured task to work through on their own devices:
Part A — Step-Up Switch to Step-Up mode. Record the default N₁, N₂, and output voltage. Now drag N₂ from 150 up to 200. What happens to the output voltage? What changes in the diagram?
Part B — Step-Down Switch to Step-Down mode. Record N₁, N₂, and output voltage. Drag N₁ up to 200 while keeping N₂ at 50. What happens? Why does the bulb appear dimmer?
Part C — Find the pattern Complete this table using the sliders to set the values:
| N₁ | N₂ | Turns Ratio | Vs (calculated) | Vs (simulation) |
|---|---|---|---|---|
| 50 | 150 | 1:3 | ||
| 100 | 100 | 1:1 | ||
| 150 | 50 | 3:1 | ||
| 40 | 200 | 1:5 |
Students fill in the calculated column using Vs/Vp = N₂/N₁, then verify against the simulation. Any discrepancies reveal a calculation error to self-correct immediately.
Key Discussion Questions
- Why does increasing N₂ increase output voltage — what is physically happening in the core?
- If a step-up transformer increases voltage, does it create extra energy? What must happen to current? (Conservation of energy — leads into P = IV)
- Why do power stations use step-up transformers before transmitting electricity across the National Grid?
- Why do your household appliances need step-down transformers built into their plugs?
Plenary (5 min)
Pose this exam-style question verbally: “A transformer has 400 turns on the primary and 2000 on the secondary. The input voltage is 230 V. Calculate the output voltage and state whether it is step-up or step-down.” Students write answers on mini whiteboards, then verify using the sliders. The simulation confirms the answer visually — they should see many more loops on the secondary side.
Real-World Links to Mention
- Power stations step voltage up to 400,000 V for National Grid transmission — reducing current enormously and cutting energy lost as heat (P = I²R)
- Local substations use step-down transformers to bring voltage back to 230 V for homes
- Phone chargers, laptop adapters, and electric toothbrush bases all contain step-down transformers
- MRI scanners and X-ray machines use step-up transformers to achieve the very high voltages their equipment requires