# electromagnet pull

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#### sfx81

##### New Member
Hi. Here is the data for electromagnet
Wire material = copper
Turns = 160
AWG = 22
Iron Core = Steel bolt, ¾-13 thread, 2” long.
Resistance = 0.65 Ohms.
I = v/r = 9/ 0.65 = 13.84A

So If I connect typical 9V 200mA battery, how can I calculate how much weigth it can pull and for how long.

Any help will be appreciated.
Thanks
Kazz.

#### blueroomelectronics

##### Well-Known Member
Those tiny 9V batteries won't last long plus their internal resistance will keep it from having any real current. You need a more power battery.

#### MrAl

##### Well-Known Member
Hi. Here is the data for electromagnet
Wire material = copper
Turns = 160
AWG = 22
Iron Core = Steel bolt, ¾-13 thread, 2” long.
Resistance = 0.65 Ohms.
I = v/r = 9/ 0.65 = 13.84A

So If I connect typical 9V 200mA battery, how can I calculate how much weigth it can pull and for how long.

Any help will be appreciated.
Thanks
Kazz.

Hi,

We had a rather involved discussion on building an electromagnet in this
forum a while back. You could do a search to find it if you like.

One of the conclusions was that the electromagnet is strongest when
the resistance of the coil matched the internal resistance of the battery.

#### colin55

##### Well-Known Member
The pull of an electromagnet depends on a number of things. No only the amp-turns but the material of the core, its saturation, the size of the core and whether the opposing end is brought around to form a horseshoe.
It also depends on the material and thickness of the "pole piece" and the contact distance between the poles and the pole piece. These things will make a difference of more than 10:1

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