9 replies to this topic

[okeeg001]

I've been sent here with my tail between my legs. I posted this in the wrong section, sorry David

Can anyone help me? I've got to write about how different thicknesses of wire affect the current, but I can not got a clue! If anyone is good at physics would you help me?


Many thanks

[adslegend]

I imagine David actually intended to move the thread for you but forgot. Or perhaps his Pringles tube suddenly sprouted legs and ran off, thus rearranging his order or priorities.

Anyway, I answered in your other thread

[Hairbearuk]

I've been sent here with my tail between my legs. I posted this in the wrong section, sorry David

Can anyone help me? I've got to write about how different thicknesses of wire affect the current, but I can not got a clue! If anyone is good at physics would you help me?


Many thanks

the best way to explain it is that the thicker the cable (wire) the higher amount of electrons that flow along it (hence having higher current ratings) a bit like plumbing really; the bigger the water pipe, the more water can flow through it. This is then affected by the number of taps that are connected to it.

Which is why circuits have current ratings.. if you have too much power (current in Amperes) being drawn from it, the electron flow is too high, hence the cable becomes warm, or simply the fuse blows protecting the circuit..

Does that help??

HB

[Capt. Carrot]

I imagine David actually intended to move the thread for you but forgot. Or perhaps his Pringles tube suddenly sprouted legs and ran off, thus rearranging his order or priorities.

Anyway, I answered in your other thread

Oi, Adslegend, get off out of it and do some revision.

[okeeg001]

Thank you everyone I think I understand know

[adslegend]

Oi, Adslegend, get off out of it and do some revision.

I'm done for the day boss

[PontiacFirebird]

By the way, what's SWG? I've never heard of that before..

A useful equation to help you out:

Resistivity (of a wire) = [Effective Resistance (in circuit) x Length of wire] / Cross sectional area of the wire. Or Rho=RL/A

You could say that if the cross sectional area of the wire is large, it will make the resistivity smaller.

[Damsel]

By the way, what's SWG? I've never heard of that before..

SWG in this context is Standard Wire Gauge. Basically, it relates to the thickness of the wire.

Edited by Damsel, 18 January 2010 - 07:16 PM.

[TallGuy]

You will also find that the distribution of electron flow (current) is not uniform across the CSA of the cable as more of it flows towards the outside. In fact depending on the application you might just as well use a tube as the middle isn't doing much.

There is also a difference in current carrying capability between solid core and multi-strand. Be aware that if you need to draw say 10A but you only have 1A cable you can't just use 10 cables in parallel and bundle them together as the current carrying capability of 10x1A cables in a bundle is not 10A due to de-rating factors.

A good source for information is from Tyco Electronics (formerly known as Raychem) in Swindon. They have a wealth of information on-line with application notes and guides.

[Rocket]

Wire guage tends to be in mm2 in UK and Europe now, instead of SWG we tend to use CSA (Cross Sectional Area)2 (squared)

For instance I stock a cable that has a CSA of 4.0mm2 and is rated at 40 Amps.