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# Does the strength of the electromagnetic field of a coil depends upon the thickness of the wire? Answered

Whenever I have problems with the magnetic field strength of an electromagnet people tell to use a finer wire, I have some, its thickness is not more then the thickness of a hair, but whenever I use it, I have difficulty in connecting it with the battery because it's so thin it easily breaks off, and when I turn on the switch, it burns up instantly, maybe I am not using enough length of it. So does the field strength really increase with the decrease in thickness of the same length of the wire and same diameter of the coil, if it does than why?

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It does not depend on the thickness of the wire. Well, not directly.

As steveastrouk wrote, the magnetic field depends on the current through the wire and how often the wire goes around the core - the number of loops.

If you use a thinner wire, you can wrap more turns into a given space. Good for the magnetic field!  But...

A thinner wire means more resistance. More turns mean a longer wire and that means even more resistance.  More resistance means that a given voltage can drive less current through the wire. Less current means a lower magnetic field.

If and when the two effects cancel each other, well that's what math is for.

(Of course you could increase the voltage to keep the current in the thinner wire the same as in the thicker wire, but that would increase the thermal losses in the wire as well.)

So, it's best to use a thick long wire, but I think the diameter of the coil should also affect the magnetic field strength, because a wire of same length will have more turns around a core of lesser diameter, and less turns on a core of greater diameter, is this right? I did an experiment, I wrapped some wire around a hollow tube of very small diameter and I wrapped the whole wire in about 2 cm of length, the strength of the field was good, then I wrapped the same wire on the same tube but along the length of the tube, which was about 30 cm, now the field was relatively weaker, maybe it was because the number of turns per unit length was decreased.

I also wrapped the same wire on a tube of diameter about 15 times larger then the diameter of the previous tube and the field strength was very very weak,

So, I came to know that a long thick wire wrapped around a core of small diameter and small length produces the strongest magnetic field if the current and voltage remains constant.

That's right, the AREA of the coild affects the field STRENGTH, but the FIELD is only determined by the number of turns and the current.

i want to know what will happened to a induction motor,when winding the starting coil with thinner diameter wire and increase the number of turns

How to control the temperature of the coil when we give more voltage to pass more current through the coil and to produce more magnetic field strength?

It only matters on the current and how many times you coiled it.

No, what matters is the current and the number of turns, it isn't affected by the thickness of the wire.

Does the overlapping of turns has any effect on the field's strength?

No, assuming they're all still wound in the same direction !

I once made an electromagnet, first I wound, say from point A to B along the length of the rod, but still there was much wire left, than I started winding over the previous winding from point B to A, so what happened to field in this case?

It would have been bigger than one layer, the current was still passing down the coil in the same direction.

There are also special, high temperature rated wires for making coils like this, but you have even more maths to work out the maximum temperature inside the coil - though you can find maths for it in books.

In the LIMIT we reach the requirements for a Florida-Bitter coil, where cooling water is pumped at high speed THROUGH the windings !