Faraday's Law & Lenz's Law

Here we derived a formula for the force between two current carrying wire. If the direction of the current were opposite, the force would be outward. When current constantly switches directions, the net force is zero because they cancel each other out.

The graph below predicts how the magnetic field changes as the angle changes. The graph is a sinusoidal wave. 

 This is a close up of Prof. Mason showing the class that a current wire with many loops creates a larger magnetic field. The magnet moving in and out of the current loop changed the magnetic field as well. The magnet moving in and out of the loop causes an induced current. The quicker Mason  moved the moved, the greater the current was. We saw this increase in current through the use of the Galvanometer.

Here we saw that an inductor acts this way as well.

In this activity, we used a magnetic field sensor, loops of wire parallel to the flat end of the magnetic field sensor, and a test tube to determine the magnetic field at the center of a current loop.

The graph shows the magnetic field increasing per loop added.

The measurements for the number of loops. current, voltage and magnetic field are in the table below. The magnetic field increases with the number of coil turns.

This is a magnetic field sensor used in this activity.

Here is a comparison of the magnetic flux graph vs time and the emf graph vs time.

Below is an image of the device Prof Mason used to demonstrate how an insulated coil in contact with another causes an induced current due to the alternating magnetic fields. The device was connected to a bulb that got dimmer or brighter when the coil was moved. 

Without contact, the wireless charging created an alternating current which created an alternating magnetic field. This alternating magnetic field created a magnetic field in the coil and an induced alternating current that lit the bulb. 

Mason next showed us how opposing magnetic fields causes metal objects to move. He compared the movement of a copper ring, aluminum ring and silver ring. The aluminum ring moved up the most because it is less dense than silver or copper. The copper moved the least due to its higher density.

Magnetic fields can be made larger if the magnetic moves faster, the radius of the loop is increased, the size of the solenoid is increased or the length of the coil is increased.

Below is diagram of the direction of the magnetic field and current of the device previously used above. 

Below is a diagram of a magnet falling through an aluminum tube. As the magnet falls it creates a current in the counterclockwise direction. This current caused an upward magnetic field. This caused the magnet to move very slowly down the aluminum tube.  

This video shows the magnet falling slowly down the tube.

Summary:

• Current carrying wire creates a magnetic field that induces an electromotive force in the second coil.
• When a magnet moves in and out of a current loop, it creates an induced emf.
• Magnetic fields can be made larger if the magnetic moves faster, the radius of the loop is increased, the size of the solenoid is increased or the length of the coil is increased.