Transformer Simulator: Turns Ratio, Losses & Efficiency
Build a step-up or step-down transformer, add winding resistance and core loss, and watch efficiency change as you load it.
About the Transformer Simulator: Turns Ratio, Losses & Efficiency
Free transformer simulator: turns ratio, losses & efficiency. Build a step-up or step-down transformer, add winding resistance and core loss, and watch efficiency change as you load it. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for engineering, the transformer simulator: turns ratio, losses & efficiency 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.
Build a step-up or step-down transformer, add winding resistance and core loss, and watch efficiency change as you load it. 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 Transformer Simulator: Turns Ratio, Losses & Efficiency
- Use the controls to change Primary turns Np, Secondary turns Ns, Primary voltage Vp (RMS), Load resistance, Winding resistance (each side), and more. The simulation reacts instantly.
- Press "Step-down (wall to device)", "Step-up (grid transmission)", "Near-ideal (low loss)" 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
- Set Ns greater than Np and confirm the readout switches to step-up with a raised secondary voltage.
- Push the winding-resistance slider up and watch the secondary voltage sag below the ideal Vp×(Ns/Np) value.
- Raise the core-loss slider with a light load and see efficiency fall even though the copper loss barely changes.
- Try the Near-ideal preset, then the high-loss settings, and compare the power breakdown bar in both cases.
Key ideas you can learn
- An ideal transformer's secondary voltage is set only by the turns ratio: Vs = Vp×(Ns/Np).
- A transformer with more secondary turns than primary turns (Ns > Np) is a step-up transformer; fewer secondary turns (Ns < Np) makes it step-down.
- Real windings have resistance, so some voltage is lost to I²R heating in the copper, and the secondary terminal voltage sags a little below the ideal value under load.
- Core (iron) losses come from magnetizing the core back and forth every cycle (hysteresis) and from small circulating currents inside the core (eddy currents); unlike copper loss, they are present even with no load connected.
- Overall efficiency is output power divided by input power, and it drops as either the winding resistance or the core loss increases.
- Because power = voltage × current, stepping voltage up trades it for a proportionally lower current — which is why long-distance power lines use very high voltages to keep transmission current, and I²R losses, low.
Ideal secondary voltage: Vs = Vp × (Ns / Np)
Secondary current: Is = Vs / Rload (found after accounting for winding drop)
Primary current (ideal): Ip = Is × (Ns / Np), adjusted here for winding and core losses
Copper loss: Pcu = Ip²Rp + Is²Rs Core loss: here modeled as a percentage of the throughput power, for an intuitive slider — in a real transformer it is closer to a fixed amount that barely changes with load
Efficiency: η = Pout / Pin = Pout / (Pout + Pcu + Pcore)
Voltage regulation: VR% = (Vs,no-load − Vs,full-load) / Vs,full-load × 100 — how much the secondary voltage sags once current flows through the winding resistances. A near-ideal transformer (low Rw) has a small VR%; a lossy one sags more under load.
Where this is used in the real world
Transformers step voltage up for long-distance power transmission and down again for homes and factories, and smaller versions live inside phone chargers, doorbell transformers, welders, and the isolation transformers used in hospitals and labs.
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 do power grids transmit electricity at high voltage?
Transmitting the same power at a higher voltage means a lower current, and since resistive loss grows with the square of current (I²R), high-voltage transmission loses much less energy to heat in the lines. A step-up transformer raises the voltage for the transmission line and a step-down transformer lowers it again near homes.
Why isn't a real transformer 100% efficient?
Two things eat into the power: copper loss (I²R heating in the primary and secondary windings, which grows with load) and core loss (energy spent magnetizing and demagnetizing the iron core every cycle, which is present even at no load).
How do you tell if a transformer is step-up or step-down?
Compare the turns: if the secondary has more turns than the primary (Ns > Np) it is step-up (raises voltage, lowers current); if the secondary has fewer turns (Ns < Np) it is step-down (lowers voltage, raises current).
Is the Transformer Simulator: Turns Ratio, Losses & Efficiency 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 Transformer Simulator: Turns Ratio, Losses & Efficiency 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.