Faraday's law: Lab examples of AdB/dt

 Faraday's law says that there is an induced voltage (emf) created if you change the magnetic flux through a conductor. Mathematically, this is induced voltage = d(BA)/dt, since flux is magnetic field times the area it flows through. 

One way to cause a change is to change the B-field through an area, or emf = A dB/dt. To see the math for this case, check this video out. 

Here are some lab examples where we see this happening. By the way, the physical reason why and how this works is that whenever you change a magnetic field, it induces a circulating electric field! It is an E-field that is turning on the current in the loops of wire and metal!