Why is resistance directly proportional to length

After all, if resistance occurs as the result of collisions between charge carriers and the atoms of the wire, then there is likely to be more collisions in a longer wire. More collisions mean more resistance.

Second, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe. This can be attributed to the lower amount of resistance that is present in the wider pipe. In the same manner, the wider the wire, the less resistance that there will be to the flow of electric charge.

When all other variables are the same, charge will flow at higher rates through wider wires with greater cross-sectional areas than through thinner wires.

A third variable that is known to affect the resistance to charge flow is the material that a wire is made of. Not all materials are created equal in terms of their conductive ability. Some materials are better conductors than others and offer less resistance to the flow of charge. Silver is one of the best conductors but is never used in wires of household circuits due to its cost. Copper and aluminum are among the least expensive materials with suitable conducting ability to permit their use in wires of household circuits.

The conducting ability of a material is often indicated by its resistivity. The resistivity of a material is dependent upon the material's electronic structure and its temperature. For most but not all materials, resistivity increases with increasing temperature. The table below lists resistivity values for various materials at temperatures of 20 degrees Celsius. Resistance There is a resistance to the flow of an electric current through most conductors.

The resistance in a wire increases as: the length of the wire increases the thickness of the wire decreases An electric current flows when electrons move through a conductor, such as a metal wire.

Circuit with a cell, switch, lamp and ammeter connected in series The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current. As a result, resistance increases. Therefore resistance increases with the length. When cross sectional area increases the space of the elctrons to travel increases simply explained. Try formula sq rt I squared x t divided by k and it gives you 1. So a minimum CSA of 2mm is required, 2. The resistivity of a material is the resistance of a wire of that material of unit length and unit cross-sectional area.

Add a comment. Active Oldest Votes. I would really like to see a derivation of the formula above though, even a heuristic one. Improve this answer. Community Bot 1. I teach high school physics, and I'll endeavor to use this analogy in the class room. Featured on Meta. Now live: A fully responsive profile.