Dimmer Switch

this is from the same set of pictures i took last journal, mainly because i cant find my camera right now. luckily, i took a picture of the dimmer switch for my fan. because the brigthness of the light and speed of the fan are directly related the strength of the current, you can control the level of light and fan speed by lowering the current. Current equals yoltage over resistance, so this can be acheieved through changing either factor. Dimmer switches work by changing the resistenace, the denominator of the equation. therefore, in order to dim the light, the switch must increase the resistance. this is done by moving one part of the circuit up and down a strip of resistant material. since resistance icreases with length of the wire, and the resistor in this case is short, the resistance of the switch must be comparatively high vs the rest of the circuit. and although it is hard to tell from these photos, those lights are actually different brightnesses.

Motors

Someone sprayed insecticide next to my house, so my room smelled pretty bad and i turned on all the fans in my room, which reminded me of the motors from last quarter. the motors converted electrical energy into mechanical energy by using magnets and current. because current in a wire is caused by the movemnt of electrons, which ar charged particles, the magnet will either repel or pull a wire in a certain dirction. if the the wire is coiled, it can be forced to spin around an axis by rapidly switching the direction of the current so that the electron flow always goes in a certain direction relative to the magnetic field. This made me wonder though. Since my fan can operate at different speeds, that means that the current must switch directions at different rate, or the force on the coil would not be constant in direction and magnitude. So there must also be some form or current regulator in the system as well, which can actively control how fast the current switches.

Another music related post, this time about my speakers. Speakers operate using magnets, one reason why you arent supposed to put them on you computer desk near the hard drive or the screen, at least back when people still used CRT's. the magnets produce sound by affecting a n eletric coil around the center of the actual speaker. when a current is passed through the coil, the mgnets field causes a force that pushes upward. when the current reverses, the coil is pulled down. this is done rapidly to cause a vibration, which then produces a sound. to produce differnet frequencies of sound, the speaker must run current in each direction for certain amounts of time to cause a slower or faster vibration. for lower counds, the current goes in one direction for a longer period of time than higher sounds, which require a higher frequency. the speaker consists of both a permanent magnet, often neodymium, and the electromagnet of the coil.

Tangental velcoity vs angular velocity

this record player provides a good example of the differences between tangetal velocity and angular velocity as well as the difference between their respective accelerations. when i start the record player, if i track the positions of two different points on the record at different radii, i find that they rotate around the axis at the same time intervals, meaning they cover the same amount of angular displacement no matter where that spot is. however, it is apparent that the different spots have different speeds. this is the tangental velocity. if i just focus at one spot, i only see a marked point on the record pass my eyes in an instant, when it is attmpting to go forward, yet is being held in a circlular movemnt by centripetal force. this instantaneous velocity is measured in meters per second, not by angular displacement and is thus a differnt speed at different radii.