Changing magnetic polarity of an electromagnet

In summary, changing the magnetic polarity of an electromagnet involves reversing the direction of the electric current flowing through its coil. This can be achieved by altering the power supply or using a switch to change the current's flow. As the current direction reverses, the north and south poles of the electromagnet also switch places, allowing for applications such as magnetic switches, motors, and transformers. This property is essential for various technological functions, enabling control over magnetic fields in multiple devices.
  • #1
fmorgan2
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I would like to change the polarity of an electromagnet. I have reversed the wires attached to a 9 volt battery that wound about a bar magnet but this did not seem to make the north pole become the south pole.
Thanks for your assistance,
Frank
 
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  • #2
Reversing the wires is the right solution. How do you know the poles didn't change?
 
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  • #3
From what I have read, it takes a considerably strong applied magnetic field to change the direction of polarity of a permanent magnet. One way to do it with a weaker magnetic field is to heat the magnet above its Curie temperature, and then apply the magnetic field. It comes as no surprise that you could not get the poles to change with even moderately strong electrical currents in the coil of the electromagnet.
 
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Charles Link said:
to change the direction of polarity of a permanent magnet.
An electromagnet is not a permanent magnet.
 
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  • #5
The OP said electromagnet. The case with a permanent magnet Is different.
 
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  • #6
Gordianus said:
The OP said electromagnet. The case with a permanent magnet Is different.
I think the OP needs to clarify what he is using in the core. If it is a soft iron core, the polarity should simply depend on the direction of current, and he would find it a simple matter to get the polarity to reverse.
 
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  • #7
Maybe you're seeing residual magnetization of the core? As if the first current pulse magnetized it while it was killing the battery. Then when you reverse the terminals there's no (or not enough) reverse excitation?

Try a new battery or measure the current somehow. You're intuition was correct, I think. Something isn't what you think it is on your lab bench.
 
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  • #8
fmorgan2 said:
reversed the wires attached to a 9 volt battery that wound about a bar magnet
It sounds like the OP has an electromagnet wound around a permanent magnet.
 
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  • #9
It's a pity that the OP hasn't come back to answer these questions - he's been back to PF, just not this thread. So we're guessing.

I for one would like to see a detailed description of the setup. With numbers and everything.
 
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  • #10
BTW, you'll probably need a real low voltage high current power supply to do anything useful. A 9V battery just can't do much.
 
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  • #11
That's one reason I asked for numbers.
 
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FAQ: Changing magnetic polarity of an electromagnet

What is magnetic polarity in an electromagnet?

Magnetic polarity in an electromagnet refers to the direction of the magnetic field generated by the electromagnet, which has a north and a south pole. The polarity is determined by the direction of the electric current flowing through the coil of the electromagnet.

How can you change the magnetic polarity of an electromagnet?

You can change the magnetic polarity of an electromagnet by reversing the direction of the electric current flowing through its coil. This can be achieved by switching the connections of the power supply to the coil.

Why would you want to change the magnetic polarity of an electromagnet?

Changing the magnetic polarity of an electromagnet can be useful in various applications such as in electric motors, magnetic switches, and data storage devices. It allows for the control of magnetic fields to perform specific tasks, such as changing the direction of rotation in a motor or encoding information in magnetic media.

What factors affect the efficiency of polarity switching in an electromagnet?

The efficiency of polarity switching in an electromagnet can be affected by factors such as the resistance and inductance of the coil, the speed at which the current direction is switched, the core material of the electromagnet, and the overall design of the electromagnetic system.

Are there any safety concerns when changing the magnetic polarity of an electromagnet?

Yes, there are safety concerns when changing the magnetic polarity of an electromagnet. Rapid switching can cause electrical arcing, overheating, and potential damage to the power supply or the coil. Proper insulation, cooling mechanisms, and safety protocols should be in place to prevent accidents and equipment damage.

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