This week we talked about capacitance, which is (usually short term) energy storage. It is the storage of a lot of voltage but not a great deal of charge. Mr. Blake talked about two examples: the buttons on a keyboard and a touchscreen. The reason why the letters I type on this blogpost show up on the computer is because I am closing the distance between the top plate and the bottom plate when I press down. This sends a signal to the computer to type that letter. In between the top and bottom parts is dielectric material, which is an electric insulator. Touch phones, like the one above is able to function because of the same sort of idea as the buttons on a keyboard.
This week, we started learning about electric potential, which is not the same as electric potential energy. Like other energies we learned about (i.e. potential and kinetic), electric potential energy is a type of stored energy. It is energy of a charged object in an electric potential field, and it is measured in joules. Electric potential, which is also called "electric potential difference", is measured in volts, and its formula is electric potential energy divided by charge. Therefore, it can be deduced that a volt is joules per coulomb. The picture above is of a plug, which may have about 120 volts. This means that the plug has about 120 joules of energy per coulomb of charge.
This unit had a lot to do with charges. The picture above depicts this object my roommate has that sticks to the metal part of her desk with a magnet. This means that the metal on the desk and the magnet are different charges. Either positive and negative, positive and neutral, or negative and neutral. All of these combinations would result in the attraction needed for the object to stick to her desk. It's quite interesting to realize that things I see every day have something to do with physics. Also, in the upper left part of the picture, you can see part of my roommate's Justin Bieber poster. They must be different charges, because she is quite attracted to him.
This week, we discussed forces and charges. We conducted a "magic tape" lab, in which tape would be attracted to a person's hand after being pulled off a table. This occurred because opposite charges attract. In this case, the tape is attracted to the hand because the two are different charges. However, if I was to touch the tape and neutralize it, it would not be attracted to my hand. We also discussed insulators and conductors. Insulators are materials such as wood and rubber that hold on to electrons, while conductors such as metallic materials, do not.
