Unit 7 Summary- Magnetism

One of the big ideas in Unit 7 was Electromagnetic Induction. We learned about commercial applications like how credit cards work, how traffic lights work, and what goes on in those pesky TSA check points. As an overall rule in this unit, we had to understand that a change in magnetic field induces voltage and causes a current. This was fairly easy to apply to traffic lights and credit cards, but more difficult to use it when understanding generators and transformers. A generator's goal is to generate current, but there are various components that must be present for it to work. Generators work opposite of motors. A magnet passes through a loop of wire, changing the magnetic field, inducing a voltage, and causing a current. It first uses mechanical energy to spin something over coils of wire, but then changes to electrical because of electromagnetic induction. Transformers are a simpler concept, but have a few qualities. There are step up and step down transformers which allow the right amount of voltage or current to pass through and get power to a destination safely. Important formulas to remember are P-primary= P-secondary, Iv=iV. Because of this, power is conserved. By using AC current in the primary, the magnetic field in the secondary changes. Also, #loops primary/v primary= #loops secondary/v secondary.


Our second big theme was Forces on Moving Charges. Regarding cosmic rays, we learned that charges have to be moving parallel to the magnetic field to feel no force when entering the earth's atmosphere. If they are moving perpendicular, then they will feel a force from the earth's magnetic field, and will be repelled back into space. While this also pertains to Magnetic Fields, knowing that charges always flow from magnetic south to north inside the field. The right hand rule came up during this theme, and it should be noted that I-index finger-current, M-middle finger-magnetic field, and F-thumb-force. When solving problems, using this right hand rule is important to determine where the missing value is pointing. In class, we assembled small motors consisting of a battery, a magnet, paper clips, rubber bands, and a coil of wire. This electrical energy turns into mechanical energy. The current carrying wire feels a force in a magnetic field and causes a torque which causes the motor to spin.




Lastly, we discussed magnetic fields which flow from magnetic south to magnetic north. The source of all magnetism is moving charges. There are spinning electrons that are clustered into domains. The electrons can be unaligned, where the electrons are pointing in all different directions or they can be aligned where they are pointing in the same direction. Back in Chemistry, we learned that opposites attract, and like charges repel. To go further, like charges repel because the direction  of the field lines are opposite directions, and they push against each other. Likewise, opposite poles attract because the field lines are going in the same direction.