The first topic of discussion was Magnetic Fields. Magnetic fields are created by moving charges, and have a symbol of 'b'. Field lines travel from the South to the North pole inside the magnet, and from the North to the South pole around the magnet. Magnetic fields are 3D.
Magnetic fields are the reason that like poles repel and opposite poles attract. When magnetic field lines are going in different directions, the magnets repel, but when the magnetic field lines are facing the same direction, the magnets attract.
Magnetic fields are also what allows a paperclip to stick to a magnet. Before coming into contact with a magnet, a paperclip's domains (random clusters of charges all moving in the same direction) are unaligned. When brought near a permanent magnet, the magnet's b causes the paperclip's domains to align along with the magnet's b. The paperclip is now a magnet with its own North and South poles and magnetic field. Because opposite poles attract, the paper clip sticks to the magnet.
The Earth's magnetic field is interesting in that although geographic North is Canada, that region is home to the magnetic South. Thus, the magnetic field runs from Canada (the magnetic South) to Antartica (the magnetic North) inside the Earth, and from Antartica back to Canada outside of the Earth. This is the reason that the Northern Lights occur. Cosmic rays can only enter the atmosphere when moving parallel to the Earth's magnetic field. Should the cosmic rays attempt to enter the atmosphere at the equator, the Earth's b would deflect them back into space.
The last, and perhaps most obvious, part of magnetic fields are Compasses. A compass is simply a magnet that is free to move, and aligns with the direction of the magnetic field.
Below is a podcast made by yours truly about Magnetism.
The next topic was Forces on Charged Particles.
The most important thing to remember is the Right Hand Rule. Just like in the diagram, the thumb shows the direction of the force, the index finger shows the direction of the current, and the middle finger shows the direction of the magnetic field.
Also in the realm of Forces on Charged Particles are Motors. Motors consist of current carrying wire and a magnet. They convert electrical energy into mechanical energy when the current carrying wire feels a force caused by the moving charges. This force creates a torque, making the motor run. For more on motors, check out my motor blog here.
Finally we discussed Electromagnetic Induction. This occurs when there is a change in the magnetic field of a loop of wire, and voltage is induced, which, in turn, causes a current. This is seen again and again in our crazy, modern world, like in credit card machines, traffic lights, and metal detectors.
Electromagnetic Induction also allows transformers to work. A transformer is a box with two coils of wire that can either increase or decrease voltage into an appliance. They work by changing the magnetic field of the primary coil through AC, which means that the b is constantly moving and changing. This then changes the magnetic field of the secondary coil, which changes the voltage.
Faraday's Law shows us that:
Transformers can be found on power lines, computer chargers, and appliance plugs.
Generators also work because of Electromagnetic Induction. Like a motor, they require a loop of wire and a magnet. However, this is where the similarities stop. Generators convert mechanical energy into electrical energy, and in this case, either the magnets are moving around the wire or the wire is moving around a magnet.
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