Magnetic Fields, Power Lines, Levitation (5/14/2015)

Magnetic Fields

While hard to grasp from the drawing above, what is being depicted is how two magnetic fields around wires affect the field around a neighboring wire. We learned that as current is flowing, the magnetic field is flowing in a circular pattern around a wire. As we see by the circles (dots pointing outward, and x pointing inward), due to two wires near each other, the field is rotating upward on the left and downward on the right.

Now, we had to predict what direction the force is pointing in regards to two power lines with current flowing through. We predicted (incorrectly) that the force is pointing outward. The actual answer is that there is no force. The reason for this is because the current in power lines is alternating back and forth, leading to net forces cancelling out.

The Magnetic Field at the Center of a Current Loop

For this lab, we had to test the strength of the magnetic field around a wire with varying amounts of loops. The results of our data can be seen below:

The table above shows all the values we recovered, and the graph below that shows the values of B and shows that as the loops increase, the strength of B increases.

Michael Faraday's Quest

In the demonstration above, it can be seen that by inserting and removing a magnet into a loop of wire, an electrical force was able to be produced. Below are various ways in which we believe the strength of the electric field can be increased.

All are correct, and we have now established a connection between electricity and magnetism. This connection can be visually seen below:

Magnetic/Electrical Field Demonstration

Shown above is a setup which consists of two coils (with a light bulb attached to one coil), and a magnetic field in between the two (located in the grey ring between the coil and the black pole). As you can see, but simply having the magnetic field next to the coil, the light bulb has been lit. When the coil and bulb are lifted up (toward a weaker point in the magnetic field), the bulb dims due to a weaker electrical field being produced.

By looking at the next pictures shown above, we see that a metal ring is placed at the bottom of the pole. What happened next was that a current was run through the bottom coil, which created an opposing magnetic force that lifted the right upward. 

A magnetic force has been created due to the current, and the metal ring was repelled upward.

Shown above is another example of the magnetic repulsion created by the current flow.

The two depictions above show what is going on inside the demonstration.

In these final two pictures and video, we witness that when dropping two identical, non-magnetic, metal pieces down two tubes (one plastic and one metal), the piece falling through the metal tube falls significantly faster. The reasoning behind this is based on what we have been looking at above. A magnetic field is essentially being created as the metal piece moves downward. A drawing of what is going on can be seen on the top right.

Summary:

In summation, we have looked at how magnetic fields interact with one another, as well as how they can be used to create an electrical field. This ties electrical and magnetic fields, since we saw how the introduction of an electrical field created a magnetic field as well. This is what happened when the metal rings were levitated up and off of the pole during the Faraday demo.