# Maglev Magnetism A high\-school physics lesson on magnetism and electromagnetic induction: a bar magnet, a cutaway coil and a milliammeter, then a cutaway maglev car that levitates and launches\. By Numa Topic: Physics & Chemistry [Open the interactive Jig](https://ask.jig.com/j/5S8Ke993y8uk) ## Transcript ### 1. Maglev Magnetism The Shanghai maglev has carried passengers at up to 431 km/h, and no wheel touches its track\. Magnets lift it, steer it and drive it\. This bench builds that idea one step at a time\. Watch the car lift off and launch\. Drag the bar magnet, the knife switch, the two sliders or the red button to use them\. Drag anywhere else to turn the view\. ### 2. 1 · Magnetic Fields Every magnet has a north pole, a south pole and a magnetic field around it\. Field lines leave north and curve round to south, crowding together where the field is strongest\. Each compass lines up with the field\. Flip the magnet and watch them swing\. Click the magnet to flip it, or drag it along its rail\. ### 3. 2 · Current Makes a Field Current in a coil makes the same field pattern as a bar magnet\. This is an electromagnet\. With the switch on SUPPLY, slide the current up and the compasses turn further toward the coil\. Reverse it and north and south swap\. More current or more turns of wire make a stronger field\. ### 4. 3 · Moving Magnets Make Current Now the coil connects to a meter, with no battery\. The needle moves only while the magnet moves: a changing magnetic field through a coil creates a voltage\. This is induction\. Push faster for a bigger swing\. Pull out and it swings the other way\. Power\-station generators work this way\. ### 5. 4 · Lenz's Law Pushes Back The induced current always opposes the change that made it\. Push the north pole in and the near end of the coil becomes a north pole that pushes back\. Pull it out and that end turns south and pulls on it\. That push\-back is why making electricity takes work\. ### 6. 5 · Lifted by Attraction The Shanghai train doesn't float by repulsion\. Electromagnets on arms that wrap under the track pull up toward the steel above them, lifting the car until the gap is about 10 mm\. Sensors keep adjusting the current to hold that gap\. The gap is drawn larger than life\. Slide the lift power down and the car settles onto its skids\. ### 7. 6 · Riding a Travelling Wave The motor is in the track, not the train\. Coils in the track make a row of north and south poles that moves along it\. The car's magnets lock onto this moving wave and get pulled along\. Raise its frequency and the train speeds up\. Reverse it and the train brakes\. ### 8. 7 · Induction Everywhere Japan's SCMaglev floats by induction instead\. Magnets on the moving train induce currents in the track walls, and those currents push back and lift it\. In 2015 it set the train speed record of 603 km/h\. Induction also charges phones and makes most of the world's electricity\. It lifts only while moving, so it rolls on wheels until about 150 km/h\.