|MadSci Network: Engineering|
Electrical resistance results from the collision of the current-carrying charged particles with fixed particles that make up the structure of conductors. The collisions result in thermal energy (heat) in the conductor.
The resistance of a wire (or any conductor) is given by the following equation:
R = r l/A
|R||resistance in Ohms|
|r||resistivity of the wire in Ohms-meters (1.7 x 10-8 for Copper)|
|A||cross sectional area of the wire in meters2|
|l||length of the wire in meters|
As you can see from the above equation, thicker wires have lower resistance than thinner wires. This analagous to a thick water pipe vs. a thin water pipe. A thin wire carrying a given current will have a higher current density when compared with a thick wire carrying the same current. Higher current density means a higher probability of collision with stationary atoms and higher resistance.
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