Instructables

knowledge about wire which use in solenoid?

I want to make a solenoid & i am confused because i don't know that which type of wire is use which no or ohm . Actually i have a project in which I want to produce electricity  with the help of magnets or solenoid . So can u plz guide me this matter very gently 




Thank You
Ashish Dhiman

Picture of knowledge about wire which use in solenoid?
iceng2 years ago
You will certainly need to use magnet wire, which is copper wire with an
amazing coating that acts as a colored insulator and does not flake or
crack as the wire is bent or flexed into position..

The magnet wire insulation is how you can wind many turns
on a coil without overlapping wire turns making a "short circuit" 
that ends up bypassing a bunch of wired turns disrupting the solenoid.

The insulation has a temperature limit if your coil gets too hot after
prolonged power ON it can burn away some insulation causing the
dreaded short circuit.

Temperature limitation of 105° C  can be improved by using a better
( more $$ ) insulated wire like 130° C, 155° C, 180° C and 220° C
or cooling or running it intermittently.

Now you can decide how hot you can run your solenoid and how much
magnetic force you need that will get you the amp turns.

From the voltage available you can determine the wire size (diameter)
and see if the solenoid can be built as conceived.

You can add magnets if you need more force then reasonably
doable with conventional wire ampturns see pic.

A
coil3.png
This kind of wire (used for electromagnets, pickup coils, transformers, motor windings, etc) is called "magnet wire".  Almost always, it is made out of copper, and the insulation on it is very thin to facilitate winding several turns of it close together.
http://en.wikipedia.org/wiki/Magnet_wire

But you probably already knew that.

The amount of resistance in a coil of magnet wire (in ohms) can be calculated from the formula R=ρ*L/A, where ρ is the resistivity of copper, L is the total length of the wire, and A is the area of its cross-section.   In other words the total resistance of the coil depends on how long the wire is, and how thin it is.  Also there are tables with numbers for resistance per unit length for different standard wire sizes. 

For example, this table:
http://en.wikipedia.org/wiki/American_wire_gauge#Table_of_AWG_wire_sizes
includes the resistance per unit length for different AWG sizes.

For the purpose of building a coil to be part of a generator, the guiding equation is going to be based on Faraday's law, V = N*(dΦ/dt), which says the voltage V induced in the coil is proportional to the rate of change of magnetic flux enclosed by the coil (dΦ/dt) multiplied by the number of turns N.  

Just based on Faraday's law, it looks like a large N, number of turns, is desirable.  The only problem is that increasing N, tends to increase the total length of the wire, which increases the resistance R in the coil, which affects the maximum amount of power which can be drawn from the coil.   

Or another way of looking at that is to say that when R in your generator windings, and R in your load are the same size, then both of these are dissipating the same amount of power, and the efficiency is only 50%. 

So if it is a small generator, like just for driving a few LEDs, then R of the windings could probably be in the thousands of ohms, and the coil can be many turns of very thin wire.  But if it is a generator for powering your house, then the R is going to have to be much smaller, guessing just a few ohms,  which means using thicker wire, and probably fewer turns too.

For example, in this instructable,
http://www.instructables.com/id/DIY-1000-watt-wind-turbine/
uses coils with a small number of turns of very thick wire. But it uses some very powerful, and expensive (at the time of this writing)  permanent magnets too.
frollard2 years ago
Depends on the function of the solenoid and how much force it has to deliver...

more turns + more voltage = more force
More CURRENT +more turns. An important difference.