Magnetic Fields Caused By Currents

Purpose:  We begin by look at the magnetic field generated by a wire with current. We, also, look into the effects of a current a wire in the presence of a magnetic field and how we can implement this with our electric motors.

Effects Of Heating A Magnetized Object

We discussed that there are two ways to demagnetize a piece of metal. One option was to simply hit the metal. The other option was to heat it until it is demagnetized. In some cases, like the video shows, demagnetizing an object may take a lot of heat.

On the right side of our white board, we indicate how magnets are magnetic and how objects that can become magnetic are not magnetic at the microscopic level. We drew little pill like figures that have their own poles and show how they are oriented when some object is magnetic and when some object is not. When something is magnetic, the poles all face in the same direction. We also discuss electric dipole moments, which is the potential for some some closed circuit to rotate with some torque.

Electric Motors

We begin to look at how electric motors work. We see that the rotation of the motors is dependent on the current in the wire, which is dependent on the the potential difference on the power supply. Our video shows that if we switch the wiring from the batteries. the current switches direction and the motor rotates in the opposite direction. This just proves that the magnetic force is dependent of the direction of the current and the direction of the magnetic field. The reason why the motor continues to rotate and not stop like in the previous lab is because the part of the motor that is allowed to rotate has a piece of circular metal at the center axis of rotation the is sliced in half. this means that they are essentially not connected. Each wire is connected to each slice and since the slice is made of metal, current is allowed to flow through it, as the motor rotates, the slices rotate as well and the fixed wires the touch the slices disconnect from the slice and proceed to touch the next slice. This causes the torque to remain in the same direction as long as current continues to flow out of the battery in the same direction.

Our next task was to create our own motor our of one magnet, a single wire, and some plugs to connect the single wire to the battery. We rolled the wire until it had a fair amount of loops and the loop was decently sized. This had to be accounted for because we know that the moment is dependent on the amount of loops as well and the area that the loops encompass.

In our whiteboard, we indicate how that magnetic field and the current effect the way the loop rotates on the motor used previously. The motor had two sides composed of loops and the current was flowing in the same direction. 

Looking At The Magnetic Field Around A Wire With Current

Professor Mason shows us that the current in a wire creates a magnetic field around in that flows in a circular motion around the loop. We find that we can use our right hand to find the direction that the magnetic field rotates by facing our thumb in the direction of the current. Our fingers end up showing the direction of the magnetic field. This is also shown using the magnets in the video.

Professor Mason demonstrates which direction the magnetic field is going in a wire that is positioned in an intricate way. We find that the magnetic forces can simply be added.

We discuss how the magnetic force and the electric force helps give rise to the speed of light constant. We also give a representative drawing of how the magnetic field rotates around a wire of current. The circle with a dot at the center shows us that the current is directed out of the board. We also start to get into Ampere's Law. This law allows us to find the magnetic field with the currents that generate the magnetic field. This law is very similar to the way Gauss' Law, which uses the charge to find the electric field.

Conclusion:  We discussed how heating up a magnetized metal can demagnetize it, It can also demagnetize with time and by striking the metal until it is demagnetized. We, also, discuss how we can create a loop of wire with current to rotate repeatedly so that we may use it as a motor. This is done by continuously changing the direction of the current of the loops so that it does not stop at 90 degrees like it did in the previous lab. Finally, we see that a wire with current also produces a magnetic field around the wire in a cyclone manner. We found that we can get the direction of the field using the right hand rule and that Ampere's Law makes it easy to find the value of the magnetic field.