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Download Template Title - University of Oklahoma Physics
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Insulators and Conductors • Electric Circuit – Current provided by battery flows through wire, into the light bulb, through another wire, and back to the battery. • Current: flow of electrons Battery •Pencils Electric lamp (not glowing) Electric lamp (glowing) Conductor lets electrons flow Insulator doesn’t let electrons flow are a good demo, touch the wires to the wood (no light), then touch them to the graphite (the LED lights up). •Try sliding the loose ends of the wires closer & farther, it may effect the LED’s brightness -more distance the higher the resistance in the circuit. •The Multi-meter isn’t so much for the testing of conductivity in this instance, it can be but the numbers usually loose the kids. It mostly serves to show the older kids that conductivity/resistance can be directly quantified. Applications of Insulators and Conductors High-Tension wires Superconductors Zero Resistance Infinite conductivity Only at very low Temperature High-Voltage Transmission Lines: Up to 765,000 Volts Wires are Copper Insulators are ceramic (they used to be glass). High-Voltage Breakdown Insulators Computers have printed circuit boards with copper lines connecting different Silicon chips. Silicon is a semiconductor it can conduct or insulate Atoms Insulators and Conductors Free electrons from outer shells of metal atoms can move throughout material Conductors let electrons go. They travel anywhere in the material. Metal ions (+) remain stationary Insulators let electrons flow like dogs running free There are NO free electrons, electrons are shared between atoms in bonds. Insulators hold electrons close like a dog on a leash Metal ions (O) remain stationary Conductors let electrons flow like dogs running free Resistance: is like resistance to water flow in a hose. Larger diameter hose less resistance, longer hose – more resistance Voltage like pressure, current like flow Resistance • Resistance: How much the material resists the flow of electrons R=V/I • The higher the resistance, the slower the flow of electrons, the smaller the power output Higher Resistance R = ( x L) / A R - Resistance - Density L - Length A - Area Lower Resistance
