A teacher explained why by making use of a highway analogy. The an ext lanes girlfriend have, the quicker the cars go through, whereby the variety of lanes obviously represent the cable thickness and also the cars represent electrons. Straightforward enough.

But after ~ a specific point shouldn"t the wire obtain so thick, that any thickness after the doesn"t affect resistance? for example, if you have actually a 100 car going down a highway, a 4 roadway highway is walking to enable the cars to move a lot quicker than a 1 roadway one, because there room a fewer cars per lane. But a 1000 lane highway highway is going to it is in as effective as a 10000 lane one, because on both highways every automobile has its own lane. ~ a 100 lanes, the variety of lanes doesn"t administer resistance.

So why does boosting wire thickness always decrease resistance?

You are watching: How does length of wire affect resistance

electromagnetism physics
asked Aug 11 "13 in ~ 19:38

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The car analogy isn"t together a good one, because electrons don"t actually flow from one finish of the cable to the other (well lock do but extremely slowly) and it suggests there is some space between the cars, conversely, it would be much more like a traffic jam everything the width of the highway.It"s more like a line of billiard balls, and also force is applied to the an initial one, and the power is moved to the last one v all the intermediate balls (a bit like newtons cradle, return the balls don"t yes, really bounce into each other). The free electrons bounce around, sometimes being bind (see below) with the potential difference causing an mean inclination to the direction the current.

A water analogy is much better - the pipe is always full of water, and also for the very same pump (battery), the push (voltage) is constantly lower the more comprehensive the pipe, which equates to an ext flow and also a reduced resistance.

This quote native the Wiki web page on resistivity describes reasonably well:

In steels - A metal consists of a lattice the atoms, each v an outer shell of electron which openly dissociate from their parent atoms and travel with the lattice. This is likewise known together a optimistic ionic lattice.4 This "sea" of dissociable electrons enables the metal to conduct electric current. As soon as an electrical potential distinction (a voltage) is applied across the metal, the resulting electrical field reasons electrons to relocate from one finish of the conductor come the other. Near room temperatures, metals have resistance. The primary cause of this resistance is the thermal motion of ions. This acts come scatter electrons (due to disastrous interference of complimentary electron waves on non-correlating potentials that ions). Likewise contributing to resistance in metals with impurities are the result imperfections in the lattice. In pure metals this source is negligible. The larger the cross-sectional area of the conductor, the more electrons every unit length are easily accessible to bring the current. As a result, the resistance is reduced in larger cross-section conductors. The number of scattering events encountered by an electron passing with a product is proportional to the size of the conductor. The much longer the conductor, therefore, the greater the resistance. Different materials also affect the resistance.