What factors affect the resistance of a wire?

[Guest mel5017]

I'm doing this science experiment on the resistance of a wire. Factors that I have to examine are the length, thickness and the material that composed the wires. How should I set up my prac.? One of the requirements of my experiment is to include a lightglobe in my circuit. A diagram would be helpful. Thank you.

[Cap'n Refsmmat]

Another thing that affects the resistance is heat.

That's why wires cooled down with liquid helium or liquid hydrogen become "superconductors", because they lose all resistance to electricity.

[Kedas]

Also the frequency of the voltage/current through it will change it but I guess it will only be DC or low frequencies.

 

How much wire do you have and how can you measure resistance?

[pulkit]

Also the frequency of the voltage/current through it will change it but I guess it will only be DC or low frequencies.

"Skin Effect"

 

How much wire do you have and how can you measure resistance?

A standard ohm-meter should suffice I think

[5614]

[Kedas]

A standard ohm-meter should suffice I think

 

I wasn't asking what could be needed I wanted to know what he/she had to work with

[YT2095]

1) Diameter

2) length

3) material

4) Temperature

 

that`s for basic DC resistance, it gets ALOT MORE complicated when it`s at a frequency though.

[5614]

those are all covered in my project on this; please feel free to ask me, i took the deepest look into the length, but all aspects above mentioned by yt2095 are all included.

[Guest Ismael]

diameter and length can be simplified....what really matters there is the total surface area of the wire (especially since that's where the electrons are doing their movement).

[5614]

surface area???

 

I am 100% certain that it is the area which counts, not the surface area!

the area through which the electrons travel down, the area of the wire itself, where it collides with atoms, that is resistance.

 

(surface area = outter part

area = inner part )

[YT2095]

surface area does play a part at high frequencies however, look up "Skin Effect". in fact it`s actualy a waste of time to use solid core conductors, tubing is far more efficient

[5614]

yes, but we're talking about what effects the resistance, not the skin effect, as far the original experiment is concerned, its the area.

[YT2095]

you`re talking about "electrons" and made a sweeping generalisation that was only part true, I added the the rest so that no one gets confused.

[5614]

true, i made a generalisation, but [as this whole conversation is] in aid of the original person who started the thread, for his experimental purposes - what effects the resistance of a wire - surface area is irrelevant, whereas area is VERY relevant.

 

on reading post #9 this immeditaley came to mind, resulting in my following post, sorry for the generalisation though!

[Thales]

Atomic density plays a significant role I'm reasonably sure.

[Kedas]

Atomic density plays a significant role I'm reasonably sure.

 

if you want to go one level lower then you missed the most important one, the electron configuration of an atom.

 

You will easily find the good conductors on the periodic table.

http://web.mit.edu/3.091/www/pt/pert7.html

 

BTW the internet seems to have a few tables:

http://www.chemistrycoach.com/periodic_tables.htm

[5614]

woa, that 2nd link -- i thought maybe you'd found one or two periodic table, there aint half a hell of a load there!

 

that 1st link is very good though.

 

atomic density:

makes a difference because more atoms in the wire means more atoms for the electrons to bump into, this is is resistance.

 

temperature:

makes a difference because if the atoms are vibrating loads [vibration in atoms = heat] then the atoms are effectively taking up more space, so theres more collisions, resulting in more resistance.... thats why some super-conductors work at as near absolute zero [the coldest temperature possible], super-condutcors are wires with almost none or no resistance.

 

by the way, is this for your GCSE coursework, coz for my GCSE i had to the exact same topic as this!

[Dave]

No, superconductors have no resistance at all. They work at extremely low temperatures - I think the latest ceramic stuff works at about 30K.

[swansont]

No, superconductors have no resistance at all. They work at extremely low temperatures - I think the latest ceramic stuff works at about 30K.

 

No, they've gotten stuff to work above liquid nitrogen temperatures - 77K - for some time now. YBa₂Cu₃O_7-x superconducts at temperatures as high as 94K.

[5614]

No, superconductors have no resistance at all.

 

i knew that was coming, but as physicist have not cooled a wire to absolute zero yet, only very very very close, theoretically, the wire still had resitance, so small you cant measure it, but at temperatures like 0.5K there will still be some resistance, (theoretically) i was going to say superconductor = O ohm resistance, but then i thought someone would point this out.

[jordan]

If you don't mind me asking, what would be unique about a wire at absolute zero that would allow it to not have resistance?

[5614]

heat is vibration of atoms

resistance is electrons bumping or colliding into atoms,

 

so at absolute zero atoms dont move at all, they are so cold they dont move a single bit, it is physically impossible to get colder than that, so because they dont move, the electrons dont collide with them, so there is no resistance.

 

how do super-hot superconductors work?

 

(thats all crap, sorry, i posted that ages ago and now know its wrong.... keep reading to find out more)

[jordan]

But just because the atoms aren't moving doesn't mean nothing can hit them right? They're still there and thus can be hit.

[swansont]

i knew that was coming, but as physicist have not cooled a wire to absolute zero yet, only very very very close, theoretically, the wire still had resitance, so small you cant measure it, but at temperatures like 0.5K there will still be some resistance, (theoretically) i was going to say superconductor = O ohm resistance, but then i thought someone would point this out.

 

They haven't cooled wires anywhere close, as compared to other things that have been cooled (BEC). R for a superconductor isn't just small, it's zero.

[swansont]

heat is vibration of atoms

resistance is electrons bumping or colliding into atoms' date='[/u']

 

so at absolute zero atoms dont move at all, they are so cold they dont move a single bit, it is physically impossible to get colder than that, so because they dont move, the electrons dont collide with them, so there is no resistance.

 

No, that's not it. The superconductors aren't cooled to zero, since that's forbidden by the third law of thermodynamics.

 

Superconductivity happens because the electrons pair up (Cooper pairs) and become Bosonic, which changes their interactions with the surrounding lattice. BCS theory is the basis of superconductivity.