AboutDan Fink Expertise Though my experience is mostly in the fields of electricity, magnetism, and physics, I have a broad science background. My career is in the field of alternative power sources -- solar, wind, water and battery power. But any questions about electricity, magnetism, energy conservation, power generation, electric motors, and even general physics are very welcome--especially from kids. They ask the best questions of all! I pride myself in answering science questions accurately, with ideas for SAFE, easy experiments that kids can perform by themselves--and that let them prove the answers to their own satisfaction. I think science should be fun, and available to everyone, regardless of age.
Experience I have volunteered in our local public schools for 5 years. I currently make presentations at our schools about electricity and magnetism, with a focus on solar, wind, water and other alternative power sources. I try to demonstrate at our schools how easy it is to make electricity, with simple devices using spinning magnets and coils of wire--powered by wind, water, bicycles, gerbils...etc. And of course solar panels! I am the webmaster of Otherpower.com, an alternative energy website. I have lived 10 miles from the nearest power pole for 11 years--I make all my own electricity from scratch with sun, wind and water.
Expert: Dan Fink Date: 5/2/2008 Subject: Electricity
Question I want to ask that how does the length of a material affect the conductivity of it?
thank you
Answer Hi David. Generally we talk about resistance in a conductor, measured in Ohms, rather than conductivity, measured in Mhos (get the joke? It's for real though!). They are exact opposites of each other for the math.
The conductivity (or resistance) depends on how much conductive material you have, and what kind of metal it is. A thick wire can pass more current than a thin one. And in a circuit, the resistance will be additive. For example, let's say you have 1000 feet of thick #10 AWG wire with a resistance of 1 Ohm per 1000 feet. But you add a one-foot section of #40 AWG wire to the circuit, with a resistance of 1100 ohms per 1000 feet. Your total resistance adds up---1 ohm from the 1000 ft of thick wire, and another 1.1 ohm for the short piece of thin wire, for a total of 2.1 ohms.
