Lenz’s Law in Action: Induction Demonstrations for A-Level Physics

Lenz’s Law can feel abstract when students first meet it. The idea that “the induced current opposes the change that caused it” is a mouthful – but when you see it in action, it suddenly makes sense.

That’s why in our lab, we turn the law into a series of hands-on demonstrations:

🧲 The Falling Magnet in a Tube

Drop a magnet down a copper or aluminium tube and – instead of clattering out the bottom – it drifts slowly. The induced currents in the tube set up magnetic fields that oppose the falling magnet, creating a perfect, visible example of Lenz’s Law.

🔄 The Jumping Ring

Place a conducting ring on top of a solenoid, switch on the alternating current, and the ring leaps into the air. The changing magnetic flux induces a current in the ring, which creates its own magnetic field opposing the original – and off it goes.

⚡ Eddy Currents and Damped Motion

Swing a thick metal plate between the poles of a magnet and watch as it grinds to a halt. The eddy currents induced in the plate oppose the motion, converting kinetic energy into heat. Swap it for a slotted plate, and the effect nearly disappears – a brilliant visual contrast.

💡 Linking the Theory

Every demo highlights the same principle: the induced current always acts to oppose the change in flux. Whether slowing a fall, throwing a ring, or damping motion, Lenz’s Law ensures energy is conserved and systems resist sudden changes.

For students, seeing the law “fight back” in these dramatic ways makes induction far more than an equation in a textbook – it becomes a memorable, almost magical, part of physics.