STUCK IN PHYSICSAll simulations ↗Electromagnetic induction
Move the magnet. Follow the changing flux. Turn the view to see which way the current flows.
Look around the coil
Magnet stationaryViewing from the left
Drag to rotate · wheel or pinch to zoom · arrow keys also rotate
Magnet flux directionInduced field / conventional currentConducting coil · radius 10 cm
Magnetic flux per turn
Induced EMF
Induced current
Magnet velocity
Positive flux and induced field point right (+x). Positive EMF/current is anticlockwise viewed from the right. Rotating the camera changes the view, not the experiment.
THE CHANGE AND ITS CONSEQUENCE
Magnetic flux and induced EMF
Ready to record
Induced EMF against time
Move the magnet to start recording. Stop holds the magnet still while recording continues: flux stays constant and EMF is zero. Both graphs use the same time axis. Clear graphs starts a new trace; setup changes reset the recording. Camera rotation keeps it.
A steeper flux–time slope gives a larger induced EMF. At a flux maximum or minimum, the EMF is zero:
Read Lenz’s law, one step at a time
No induced current01
What changes?
02
How does the coil respond?
03
Which way is the current?
The induced field opposes the change in flux. It can oppose an increasing flux or reinforce a decreasing flux.
The laws behind the motion
A moving magnet changes the magnetic flux through the coil. The faster the flux changes, the greater the induced EMF. A stationary magnet gives no induced EMF in this experiment.
The minus sign is Lenz’s law: in a closed coil, the induced current creates a field that opposes the flux change. Check both faces of the coil to connect the current direction with its induced north and south poles.
Predict, then check
1. Bring a north pole towards the coil. What pole must the nearby coil face become?
2. Move the same pole away. Does the current reverse?
3. Stop the magnet close to the coil. Is flux alone enough to produce an EMF?
4. Pass the magnet all the way through. Where does the EMF reverse? Now flip the magnet and repeat.
5. Open the coil circuit. What happens to EMF and current?
About this model
The magnet moves on a prescribed path, coaxial with a fixed circular coil. Its field is approximated by a uniform line of axial magnetic dipoles, and flux is calculated around the coil. Field lines show the magnet’s external field schematically; the induced coil field is shown separately by its axial arrow.
The coil is purely resistive: self-inductance is neglected, so current follows EMF immediately and stops when the magnet stops. Magnetic braking does not change the prescribed motion. Camera rotation is an observation tool, not a physical rotation of the coil. Changing magnet strength, polarity, turns or resistance resets motion rather than modelling a switching transient. Numeric predictions are illustrative.
Physics references: Faraday’s law and Lenz’s law (OpenStax).
Explore Faraday’s and Lenz’s laws
Move a bar magnet coaxially through a circular conducting coil. Rotate the 3D view to compare the current direction from either coil face, and connect changing magnetic flux to induced EMF and the induced magnetic field.
Supports electromagnetic induction topics in IB Physics, A Level Physics, AP Physics 2 and AP Physics C: Electricity and Magnetism. The model assumes prescribed magnet motion and a resistive coil with negligible self-inductance.