Electrical Power Transformer & Transmission Line Lab
Step a generator's voltage up through an ideal transformer, send the power down a resistive transmission line, and watch the current, I²R line loss and transmission efficiency all update live against the same delivered power.
Change the step-up turns ratio, generator voltage, delivered load power and line resistance, and watch the current flow down the transmission line while efficiency updates against the same delivered power.
V2 = a·Vgen, I2 = Pload/V2, Ploss = I2²Rline, η = Pload/(Pload+Ploss)About the Electrical Power Transformer & Transmission Line Lab
Free electrical power transformer & transmission line lab. Step a generator's voltage up through an ideal transformer, send the power down a resistive transmission line, and watch the current, I²R line loss and transmission efficiency all update live against the same delivered power. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for engineering, the electrical power transformer & transmission line lab runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Step a generator's voltage up through an ideal transformer, send the power down a resistive transmission line, and watch the current, I²R line loss and transmission efficiency all update live against the same delivered power. Use it to explore engineering ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Electrical Power Transformer & Transmission Line Lab
- Use the controls to change Step-up turns ratio a = N2/N1, Generator voltage Vgen (V), Delivered load power (kW), Line resistance Rline (Ω). The simulation reacts instantly.
- Press "Reset to defaults", "Lab report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Try the 95% efficiency challenge by raising the turns ratio at the default settings.
- Try the below-1%-loss challenge by raising generator voltage or lowering line resistance without touching the turns ratio.
- Watch the current particles on the transmission line slow down as you raise the turns ratio.
- Compare the efficiency-vs-ratio curve at a high line resistance versus a low one.
Key ideas you can learn
- An ideal transformer relates primary and secondary voltage and current by the turns ratio: V2 = a·V1 and I1 = a·I2, so stepping voltage up by a factor of a steps current down by the same factor for the same transmitted power.
- For a fixed amount of delivered power P, the current needed is I = P/V, so line loss I^2*R scales as P^2*R/V^2 - doubling the transmission voltage cuts line loss to one quarter for the same delivered power.
- This is exactly why power grids step voltage up to tens or hundreds of kilovolts for long-distance transmission and step it back down near the load: the same power moves with far less current, and far less I^2R loss, at higher voltage.
- Line loss can also be cut by lowering the line resistance (thicker conductors, shorter routes) instead of raising voltage, though thicker conductors and equipment cost money too - real transmission design balances both levers.
Where this is used in the real world
Electric utilities size exactly this transformer turns ratio and conductor resistance trade-off for every transmission and distribution line, since even a fraction of a percent of I²R loss over a large power grid adds up to enormous wasted energy and cost.
Who is this simulation for?
Engineering and technology students, makers, robotics clubs and teachers of design and technology. It gives a hands-on feel for how machines behave before you build a real one.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why does doubling the transmission voltage cut line loss to a quarter instead of half, for the same delivered power?
For fixed delivered power P, the current is I = P/V, so doubling V halves the current; but line loss is I^2*R, and squaring a halved current gives one quarter of the original loss - the loss depends on the square of current, not current itself, which is why raising transmission voltage is such an effective lever.
Why can't you just always crank the turns ratio up to make transmission loss negligible?
In this simulation there is no upper limit shown, but real transformers, insulation and switchgear all become more expensive and physically larger at higher voltages, and there is a practical ceiling where corona losses, insulation breakdown risk and equipment cost outweigh the shrinking I^2R savings - so real grids pick a transmission voltage that balances loss against these other costs.
Is the Electrical Power Transformer & Transmission Line Lab free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Electrical Power Transformer & Transmission Line Lab work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.