Coil Theory

[baconandeggs]

Use a bolt wrap the wire around the threads and unscrew the bolt leaving a perfect coil

[Moon]

Oct 11, 2012 18:23:20 GMT baconandeggs said:

Use a bolt wrap the wire around the threads and unscrew the bolt leaving a perfect coil

This is something that I may well try.

I'll give it a go with a drill bit first, as I have a good few small ones and see how I get on with that method.

It won't be as perfect but I'll have a fanny around with a cocktail stick.

[FirinBlanks]

Aug 29, 2012 14:23:44 GMT domesticextremist said:

'Ahem.
This is my theory, what it is...'

(Name that sketch )

Peter Sellars
The Goon Show
I'm not sure what episode though, but I listened to it recently (if that helps)?

[domesticextremist]

[FirinBlanks]

Curses! It must have been the male high pitched voice thing that threw me, both are equally fab in my eyes though (if that helps to dig me out of the hole).

[spike74656]

I'm Afraid I'm going to have to be a pain and point out that your formula doesnt take into account different voltages.

The heat generated isn't about the resistance it is about the amps. So you would need to factor in V = IR and the power drain is about the wats for which you would need P=IV Or P=Isquared R.

And then of course there are the thermal properties of the wire, How hot it can get before it starts to do strange things like melt and break.

V = Voltage
I = Current
R = Resistance
P = Power

Of course we must ask just how accurate do we really need to be, especially if we are using variable voltage batteries that we can just tweak up and down.
Not to mention if we are measuring the resistance how many of us have regularly calibrated meters with an accuracy greater than + or - 1% down on the ten Ohm range?

[spike74656]

To clarify my previous post, Resistance does play a part along with length/type of wire but the amps are the easiest way to look at the heat generated.

[Brian]

I understand "Im afraid", but the rest went whoosh, straight over my head!

[domesticextremist]

Oct 13, 2012 22:50:14 GMT spike74656 said:

I'm Afraid I'm going to have to be a pain and point out that your formula doesnt take into account different voltages.

The heat generated isn't about the resistance it is about the amps. So you would need to factor in V = IR and the power drain is about the wats for which you would need P=IV Or P=Isquared R.

And then of course there are the thermal properties of the wire, How hot it can get before it starts to do strange things like melt and break.

V = Voltage
I = Current
R = Resistance
P = Power

Of course we must ask just how accurate do we really need to be, especially if we are using variable voltage batteries that we can just tweak up and down.
Not to mention if we are measuring the resistance how many of us have regularly calibrated meters with an accuracy greater than + or - 1% down on the ten Ohm range?

Be as much of a pain as you like

However, neither the current nor the voltage are affected by the
dimensions of the coil - they are determined by the power source.

The point of the thread is to answer the question of how many
turns does one need to achieve a target resistance, that's all.

[spike74656]

Well the dimensions of the coil determine the resistance, which in turn does affect the current assuming the power source remains the same.

But fair point it doesnt need to be considered if you are only looking for number of turns for target resistance.

The best way I have seen of doing this is to just measure the wire before cutting it and then add a length of no res wire either side. You then only coil the resistive wire around the wick and take the no res wire to the connections then you have the exact resistance you want. But I would have to agree that its a bit of a faff.