The real fun is when you see the induced emf grow as you keep on winding multiple turns of wire around the solenoid. You start unwinding or winding a few turns in the opposite sense, the induced emf starts to drop. When the same loop’s position is changed so that it does not enclose the primary solenoid, the induced emf drops again to zero. If the bunch of wires are placed vertically inside the primary, no emf is developed. Furthermore, change the frequency and notice the dependence of the induced emf. Last, the phase difference between the source and induced voltages is a clear demonstration of the time derivative of a sinusoid.
However, the metallic plate with slots experiences very less effects of the magnetic field and takes longer to come to a stop. This is because due to inconsistent surface it will not have circular electric currents and thus will not have the right magnetic field to oppose its movement against the field of electromagnet.
Barkhausen effect has many important applications today. For example, the amount of Barkhausen noise for a given material is linked with the amount of impurities, crystal dislocations, etc. and can be a good indication of mechanical properties of such a material. Therefore, it is used as a method of non-destructive testing for the degradation of mechanical properties in magnetic materials. It can also indicate physical damage in a thin film structure due to various nano-fabrication processes such as reactive ion etching.
In this demonstration, we have placed a yttrium-barium-copper-oxygen (123) superconductor inside liquid nitrogen (-196°C). As it is cooled below the superconducting transition temperature, the material becomes a superconductor and a perfect diamagnet, expelling the applied magnetic field. Because of this, when a magnet is held above the material it starts to levitate and hangs suspended in air. Gradually when the liquid nitrogen boils off and the superconductor returns to temperatures above its critical point, the magnet eventually loses its levitation and falls.
an emf is generated across its end. This emf can be detected. In this demonstration, a conductor that is connected to conducting rails is moved inside the field of an electromagnet, in an oscillatory manner. The emf generated is filtered, amplified and seen on an oscilloscope.
In the second variant of this demo, permanent magnets are placed below a coil of wire. When the current is switched on, the coil experiences a force that is perpendicular to the magnetic field. The force moves the coil either in the backward or forward direction depending upon the polarity of the magnets. If the polarity switches periodically, the coil could be rotated like a pendulum.