5/12 The Magnetic Field of a Current

Professor Mason used a magnetized paper clip to demonstrate how a piece of metal loses its magnetic field when its heated. Heating the molecules causes the poles to realign themselves back to before they were magnetized.

On the right, we have pictures of how the poles on a piece of metal are aligned when they are magnetized and when they are not magnetized. The magnetized piece of metal had all their poles aligned so that the north and south poles were pointing in the same direction. The non-magnetized one has poles pointing in all directions so the poles magnetic field cancels each other out. We were then asked how we could destroy the de-magnetize the magnetized metal. We said that if you hit it really hard or heat it up really hot, it would realign the poles back to pointing in all directions.

This is the sample motor that Professor Mason gave to each group. We noticed that for the coil to spin fast, it had to be as close as possible to the magnets on each side. They were so close that you could notice scratches on the magnet. We also noticed that it is better to have a north and south pole magnet on opposite sides of the coil to keep the coil spinning fast.

This is our motor created with a coiled piece of wire, batteries, a magnet, and a closed circuit. We found that the most difficult part of having the engine run consistently was to have the coil as close as possible to the magnet underneath it. This way we can shorten the time that the coil is in the part of the spin where there is no torque, and the momentum can easily push it to keep spinning. We also found that if we have bends on the ends of the wire, it would cause a torque in the direction of the bend causing the coil to not spin smoothly. Straightening them made it spin smoother but made it easier to fall out.

We discussed the different components that are required for a motor to run. We found that the thing that is most likely to break in a motor is the brushes as they are made out of thin plastic and are frequently used to change the direction of the motor.

The above 2 pictures are from an experiment we did if we had a current going through the metal pole in the center of a box surrounded by compasses. We found that the current produces a magnetic field causing the magnets to point in a counter-clockwise direction around the metal pole. This matches our right hand rule along a current.

This is a problem we did in class of a current going through the pattern shown above. We were asked to find the force in between the wires at the very top. We found that with the right-hand rule, the magnetic field caused by the current is going through the circuit at that point is going into the board.

We drew our predictions for the compass experiment as well as the force between the wires at the very top. From these 2 experiments, we derived equations that related the magnetic force and the force due to the electric field.