### Re: I have two questions. First, why does a thicker wire have less resistance t

Date: Sat Oct 31 16:07:19 1998
Posted By: Madhu Siddalingaiah, Physicist, author, consultant
Area of science: Engineering
ID: 909376515.Eg
Message:

Hi Danny.

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

Where:

 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.