Electricity and Magnets

In this chapter, we studied magnets and their effect on electricity. We discussed how magnets work, how the Earth's magnetic field is created, how magnets have poles, how electromagnets work, how magnets affect electrical fields, and how this can be used to power objects.

In this chapter, we discussed how magnets work. 

In a magnetized object, the domains of an object, the spin of its atoms, become aligned. The domains of a magnet determine the poles of the magnet are aligned. How aligned the domains are affects the strength of the magnet. If a person were to stick a paper clip to a magnet, that paper clip would be less magnetized than a neodymium supermagnet. The domains of an object can be aligned in several ways. One is shock. Aligning a piece of potentially magnetic metal with a magnetic field and striking it will cause some of the atoms to become aligned with the magnetic field. Another way is constant magnetization. If a strong magnet is constantly left near an unmagnetized magnet, the unmagnetized object will become magnetized in the same way as the strong magnet over time. Because of this, shipboard magnets are specially calibrated to avoid being attracted to the ship, and strong magnets must be kept away from some equipment that relies on magnets, such as computers and pacemakers. Only three metals, and compounds containing these metals, can be magnetized. These are iron, nickel, and cobalt. Other objects cannot be magnetized.

Magnets have magnetic fields because of poles. They have poles because of how its domains are aligned. If a magnet's domains are aligned, the magnetic field will go from "South" to "North" inside the magnet, and from North to South outside the magnet.

 The names North and South come from the Earth's magnetic field, as that is how the charges flow there. Thus, it became the custom to call the directions North and South. Different poles of a magnet will attract each other, and like poles will repel each other. Compasses work because they align to the Earth's magnetic field. The South pole of the needle will be attracted to the magnetic North of the Earth, while the North Pole of the needle will be attracted to the magnetic South pole of the Earth. Magnetic fields are strongest when they are perpendicular, because they are able to block the object fully and slap it aside. The field is weakest at the poles, because the field cannot block the object, and allows to pass.

The Earth's magnetic field works because the core of the Earth is solid iron, causing a large magnetic field around the Earth.

This magnetic field is important because it repels cosmic rays which cause cancer. At the Equator, the field slaps the rays aside, preventing them from getting to the surface. At the poles, the field cannot block the rays, which are visible as the aurora borealis and aurora australis. However, this means that a person at the North pole has a higher chance of getting cancer than a person at the Equator.

Electromagnets work by running an electrical current through a piece of metal. Normally, this metal is unmagnetized. However, running a current through it allows it to become a very strong magnet, as seen here.

The current causes a fluctuation in the magnetic field, causing the domains to become temporarily aligned and making the magnet very strong. 

The opposite is true as well. If a magnet is ran through or past an object that is also magnetic, the object will have a small voltage induced in it, which in turn will induce a voltage, allowing the wire to power an object. 

As seen in the picture, the magnet must move to induce a voltage. If it does not, it will not cause anything to happen.

Generators use a similar process to create power. A person or machine turns a crank which is connected to a magnet with a coil of wire wrapped around it. This magnet and coil is near another magnet. When the crank is turned, the magnet and coil spin. This causes fluctuations in the magnets' magnetic fields, which causes a fluctuation in the wire's magnetic field. This induces a voltage in the wire, which in turn induces a current in the wire. This creates power, which allows the generator to power objects that need it.

Motors and transformers work in reverse of this. The coil of wire is near a magnet, and has current run through it. In the motor, this causes the coil to spin, as it is made to only receive current at certain times to allow it to spin. In the transformer, the coil is near another coil. The first, or primary, coil is wrapped a certain number of times around an object. The second, or secondary, coil is wrapped a different number of times. If it is wrapped more than the primary coil, it is a step-up transformer. If it is wrapped less than the primary coil, it is a step-down transformer. The primary and secondary coils are placed close to each other, and current is run through the primary. This causes a fluctuation in the secondary coil, which causes it to receive a voltage different from the primary coil's voltage, which induces a current different from the primary coil's current. However, the primary's current multiplied by the primary's voltage equals the secondary's current times the secondary's voltage. This process allows an object to receive more or less voltage or current if it needs it. This prevents a 12 V laptop from frying from power taken from a 120 V outlet. 

A video of transformers and generators can be seen here.

This unit was not too difficult for me. I found that it built on the last unit quite naturally, and used what I learned there in this section. While my knowledge of the workings of these concepts improved, I felt that it made more sense coming after the last unit than any other two sequential concepts this year.