The Student Room Group

Physics help needed

Hi, does ne1 know nething about resistance? I'm doing coursework and need to know why the resistance changes with the length. I've done the experimenty thing, and wrote a bit about sum sort of electron theory, but am now stuck. It appears i have to 'Use scientific knowledge and understanding to plan and communicate a procedure, to identify key factors to vary, control, or take into account, and to make a predictiom where appropriate'.....whateva that means.
Any help would be great, thanx.
1.Temperature : If the wire is heated up the atoms in the wire will start to vibrate because of their
increase in energy. This causes more collisions between the electrons and the atoms as
the atoms are moving into the path of the electrons. This increase in collisions means that
there will be an increase in resistance.
2.Material : The type of material will affect the amount of free electrons which are able to flow through
the wire. The number of electrons depends on the amount of electrons in the outer energy
shell of the atoms , so if there are more or larger atoms then there must be more electrons
available. If the material has a high number of atoms there will be high number of electrons
causing a lower resistance because of the increase in the number of electrons. Also if the
atoms in the material are closely packed then the electrons will have more frequent collisions
and the resistance will increase.
3.Wire length : If the length of the wire is increased then the resistance will also increase as the
electrons will have a longer distance to travel and so more collisions will occur. Due to this
the length increase should be proportional to the resistance increase.
4.Wire width : If the wires width is increased the resistance will decrease. This is because of the
increase in the space for the electrons to travel through. Due to this increased space between
the atoms there should be less collisions
Reply 2
Thanx SOOOOO much, that is really helpful, thanks a lot.
Dont copy and paste it now mind, :tongue: