Lab Report Day 22 - Magnetism, Motor, Forces on a Line of Charge, Compass and Magnetic Demo

2 ways to destroy a Magnet

We talk about how to destroy magnetic. We just need to make the electrons not in order. 

Magnetism

In this demo, Professor Mason has two coils of wire that can become magnetic when connect to a power supply.  A switch is attached to the two coils to change the direction of magnet. When the switch is on or off, it oscillates and stop. In order to keep the magnet spinning, we need to keep switching it to on and off. This is how a motor works.

In a two pole motor like the one above, we have to turn on and off ourselves. However, in a 3 pole motor, there is always some torque and it will keep working forever as long as there is power supply connect to it. This is how a motor work. 

Motor

Next, we are given a motor that is powered by electric current and magnetic field. Two magnets are places with opposite poles in order to power the motor. A commutator stops the current from going through as it spins. Without a commutator, it will just wiggle back and forth. The commutator makes it spin around by reversing the magnetic field for a split second allowing it to turn. 

When power supply is applied, the motor turns one way. When the power supply is reversed, the motor turns another way. 

From this model, we can see that direction of current flow dictates the direction of the motor.

Next, we were only given a magnet, two paper clips, a cup and a power source. We will make our own commutator by sanding down 360 degrees around the wire on one side while only sanding down half of the other side. This allows the current to stop every half turn. We have get a chance to make it work well. 

 Magnetic Field 

We place compasses around a metal rod when there is current going through it. The picture below shows that when the current is coming out of the page, the magnetic field is counter-clockwise around the current. When the current is going into the page, the magnetic field goes around the current is clockwise . Using this, we can construct a right hand rule where your thumb points where the current is going and the way that your fingers curl show where the magnetic field is. 


When there is only one wire, the magnet points toward the wire. Within the wires the magnetic fields cancel each other.  And when the wires are in in parallel, the magnetic field will be doubled. 
Based on observation, we can conclude that a line of current produce a circle of magnetic field, and a circle of current produce a line of magnetic field. 

Summary:

We learn the how current can affect magnetic field. We learn how motors work and we are able to build our own motor. We can apply right hand rule in more situations.