![Lenzs Law (H16) [5K20.25] @MITPIRL](https://i.ytimg.com/vi/yl6XtJ6vELU/hqdefault.jpg)
Uploaded June 2012 | Updated September 2026, 2 weeks ago
Two bar magnets of the same size are dropped through an aluminum tube and a glass tube. The magnet dropped in the glass tube falls at the normal rate of acceleration due to gravity, but the magnet falling through the metal tube is slowed.
This slowed acceleration occurs because the falling magnet induces currents inside the metal tube. The induced currents then produce a small magnetic field that opposes the direction of the original magnetic field. This effect is known as Lenz's Law, a result of Faraday's law of induction.
Two bar magnets of the same size are dropped through an aluminum tube and a glass tube. The magnet dropped in the glass tube falls at the normal rate of acceleration due to gravity, but the magnet falling through the metal tube is slowed.
This slowed acceleration occurs because the falling magnet induces currents inside the metal tube. The induced currents then produce a small magnetic field that opposes the direction of the original magnetic field. This effect is known as Lenz's Law, a result of Faraday's law of induction.
![Lenzs Law (H16) [5K20.25]](https://i.ytimg.com/vi/yl6XtJ6vELU/mqdefault.jpg "Lenzs Law (H16) [5K20.25]
Two bar magnets of the same size are dropped through an aluminum tube and a glass tube. The magnet dropped in the glass tube falls at the normal rate of acceleration due to gravity, but the magnet falling through the metal tube is slowed.
This slowed acceleration occurs because the falling magnet induces currents inside the metal tube. The induced currents then produce a small magnetic field that opposes the direction of the original magnetic field. This effect is known as Lenzs Law, a result of Faradays law of induction.")
![Break Down of Air (D29) [5A50.30]](https://i.ytimg.com/vi/ynngFTTIA2I/mqdefault.jpg "Break Down of Air (D29) [5A50.30]
Grounding rod tips of different sizes are used to discharge a large Van de Graaff generator. The larger the curvature of the tip, the more charge must build up to break down the air, resulting in longer sparks. The electricity ionizes air molecules, releasing quick flashes of light.
A pointed tip barely sparks at all, but instead creates an electric field so strong that it forms a tiny ball of plasma just beyond the tip. This is known as St. Elmos Fire, and is just visible when all the lights are turned off.")
![Coupled Air Carts (C20) [3A75.10]](https://i.ytimg.com/vi/zlzns5PjmJ4/mqdefault.jpg "Coupled Air Carts (C20) [3A75.10]
Two or more air carts are connected by springs on an air track. When this system is at resonant frequency, symmetrical patterns called normal modes appear. The normal modes are shown in both undriven and driven cases. In the undriven examples, the normal modes are found by placing the carts at certain distances from each other and then letting them oscillate. In the driven examples they are found by driving the system with a motor, and varying the frequency until the normal mode patterns appear. Both of these methods are shown for systems of two, three, and five coupled carts.")
