Science+Project

Topic: What wold the world use if we ran out of copper, silver, and gold to conduct electricity ?

Hypothesis: Dr.Robinson thinks aluminum is cheaper than the ones me mostly use and can conduct as much as them (copper, silver, and gold)
The electrons of different types of atoms have different degrees of freedom to move around. With some types of materials, such as metals, the outermost electrons in the atoms are so loosely bound that they uncontrollably move in the space between the atoms of that material by nothing more than the influence of room-temperature heat energy. Because these almost unbound electrons are free to leave their respective atoms and float around in the space, they are often called //free electrons//. In other types of materials such as glass, the atoms' electrons have very little freedom to move around. While external forces such as physical roughness can force some of these electrons to leave their respective atoms and transfer to the atoms of another material, they do not move between atoms within that material very easily. This relative mobility of electrons within a material is known as electric //conductivity//.  In physics and electrical engineering, a **conductor** is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons. Here are a few common examples of conductors: silver, gold, aluminum, iron, steel, brass, bronze, mercury, graphite, dirty water, and concrete. All conductive materials DO NOT have the same level of conductivity.

Electrical conductivity is similar to the transparency of certain materials to light: materials that easily "conduct" light are called "transparent," while those that don't are called "opaque." However, not all transparent materials are equally conductive to light. Window glass is better than most plastics, and certainly better than "clear" fiberglass. So it is with electrical conductors, some being better than others. For instance, silver is the best conductor in the "conductors" list, offering easier passage for electrons than any other material cited. Dirty water and concrete are also listed as conductors, but these materials are substantially less conductive than any metal. As each electron moves uniformly through a conductor, it pushes on the one ahead of it, such that all the electrons move together as a group. The starting and stopping of electron flow through the length of a conductive path is virtually instantaneous from one end of a conductor to the other, even though the motion of each electron may be very slow. An approximate analogy is that of a tube filled end-to-end with marbles: The tube is full of marbles, just as a conductor is full of free electrons ready to be moved by an outside influence. If a single marble is suddenly inserted into this full tube on the left-hand side, another marble will immediately try to exit the tube on the right. Even though each marble only traveled a short distance, the transfer of motion through the tube is instantaneous from the left end to the right end, no matter how long the tube is. With electricity, the overall effect from one end of a conductor to the other happens at the speed oflight: a swift 186,000 miles per second!!! Conductivity can be inferred by measuring the resistance. If you hook up a sample to be tested to a voltage source and measure the current going through the sample and the voltage across the sample, the resistance can be calculated from Ohm's law: R = E/I where R is resistance in ohms, E is voltage in volts and I is current in amperes. Once you have resistance, you can calculate resistivity. Resistivity is a factor, which when multiplied by the length of the sample and divided by its cross-sectional area, will yield the resistance. Conductivity is the reciprocal of the resistivity. The higher the conductivity, the easier it is to pass a current through the material.

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