Changing magnetic polarity of an electromagnet

Click For Summary

Discussion Overview

The discussion revolves around the process of changing the polarity of an electromagnet, specifically addressing the challenges faced by the original poster (OP) when attempting to reverse the polarity by reversing the connections to a 9-volt battery. The conversation includes technical explanations, clarifications about electromagnets versus permanent magnets, and suggestions for troubleshooting the OP's setup.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Frank, the OP, states that reversing the wires did not change the north pole to a south pole.
  • Some participants affirm that reversing the wires is the correct approach but question how the OP determined that the poles did not change.
  • One participant notes that a strong applied magnetic field is typically required to change the polarity of a permanent magnet and suggests heating the magnet above its Curie temperature as a method to change polarity.
  • Another participant emphasizes that an electromagnet is different from a permanent magnet, implying that the OP's situation should allow for polarity change with the correct setup.
  • There is a suggestion that the OP clarify the type of core material used, as a soft iron core should allow for easy polarity reversal based on current direction.
  • One participant proposes that residual magnetization might be affecting the OP's results, suggesting that a new battery or current measurement could help diagnose the issue.
  • Another participant speculates that the OP may have an electromagnet wound around a permanent magnet, which could complicate the polarity change.
  • There is a call for the OP to provide more detailed information about the setup, including numerical data, to facilitate better assistance.
  • One participant mentions that a low voltage high current power supply would be more effective than a 9-volt battery for this application.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of the OP's method and the nature of the electromagnet's core. There is no consensus on the specific reasons for the OP's difficulties, and the discussion remains unresolved regarding the exact setup and conditions affecting the polarity change.

Contextual Notes

Participants note potential limitations in the OP's setup, including the type of core material and the power supply used. There are also unresolved questions about the OP's experimental conditions and measurements.

fmorgan2
Messages
1
Reaction score
0
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
 
Physics news on Phys.org
Reversing the wires is the right solution. How do you know the poles didn't change?
 
Reply
  • Like
Likes   Reactions: vanhees71, Vanadium 50 and DaveE
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.
 
Reply
  • Like
Likes   Reactions: Dale
Charles Link said:
to change the direction of polarity of a permanent magnet.
An electromagnet is not a permanent magnet.
 
Reply
  • Like
  • Love
Likes   Reactions: vanhees71, Vanadium 50 and Charles Link
The OP said electromagnet. The case with a permanent magnet Is different.
 
Reply
  • Like
Likes   Reactions: vanhees71
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.
 
Reply
  • Like
Likes   Reactions: vanhees71
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.
 
Reply
  • Like
Likes   Reactions: vanhees71 and Charles Link
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.
 
Reply
  • Like
Likes   Reactions: vanhees71 and Charles Link
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.
 
Reply
  • Like
Likes   Reactions: vanhees71 and Charles Link
  • #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.
 
Reply
  • Like
Likes   Reactions: vanhees71
  • #11
That's one reason I asked for numbers.
 
Reply
  • Like
Likes   Reactions: vanhees71

Similar threads

Graduate Magnetization and magnet poles
  • · Replies 10 ·
Replies
10
Views
2K
High School EMF induced by Bar Magnet falling through a Coil
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad Sudden polarity reversal in opposing permanent magnets?
  • · Replies 6 ·
Replies
6
Views
5K
Undergrad How induction works within a coil (nuances of it)
  • · Replies 6 ·
Replies
6
Views
2K
High School What is the principle of a magnet?
  • · Replies 14 ·
Replies
14
Views
2K
High School Is the Direction of Magnetic Fields Truly Conventional?
  • · Replies 6 ·
Replies
6
Views
2K
High School Understanding magnetic flux change during the falling of magnet
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Magnetic field strength of a stack of magnets
  • · Replies 7 ·
Replies
7
Views
4K
High School Magnetic fields attracting two disc-shaped magnets
  • · Replies 11 ·
Replies
11
Views
3K
High School Magnet inside a solenoid with current
  • · Replies 7 ·
Replies
7
Views
2K