Flux and EMF Graphs
The relationship between a flux–time graph and the EMF it produces is a standard exam topic and a standard source of confusion. This simulation draws both graphs side by side in real time, so the link between the slope of one and the height of the other is unmistakable.
How to use this simulation
- Select different flux–time shapes, including sinusoidal and linear ramps
- Change the number of turns in the coil
- Pause at any instant to read both graphs together
What to look for
- EMF peaks line up with the steepest parts of the flux curve
- EMF crosses zero exactly at the maxima and minima of the flux graph
- A sinusoidal flux gives a sinusoidal EMF shifted by a quarter of a cycle
The physics behind it
Faraday's law states that induced EMF equals the negative rate of change of flux linkage, ε = −N·dΦ/dt. The EMF graph is therefore the gradient of the flux graph, inverted. Where flux changes steeply the EMF is large; where flux is momentarily constant — at a peak or trough — the EMF passes through zero.