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Thread: Electromagnet not repelling neodymium magnet

  1. #1 Electromagnet not repelling neodymium magnet 
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    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?


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    Quote Originally Posted by JeromeONeill View Post
    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?
    Is the Neodymium magnet shaped like a bar magnet?
    Float the electromagnet on water and approach the neodymium magnet from various angles and see it the electromagnet rotates.
    The charger does that produce a continuous current or an alternating current? Or is it pulses of current" When there is no current the core of your magnet could be attractive to your neodymium magnet. What is the core made of?


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    Quote Originally Posted by Robittybob1 View Post
    Quote Originally Posted by JeromeONeill View Post
    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?
    Is the Neodymium magnet shaped like a bar magnet?
    Float the electromagnet on water and approach the neodymium magnet from various angles and see it the electromagnet rotates.
    The charger does that produce a continuous current or an alternating current? Or is it pulses of current" When there is no current the core of your magnet could be attractive to your neodymium magnet. What is the core made of?
    Yeah the neodymium magnet is cuboid shaped. I'm not sure what the type of current is being produced, I assumed it was a continuous D.C source seeing that it is for charging a car battery, that I'll have to look into . The core is made of a 4" steel nail. Ok thanks for the help I will try all that.
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  5. #4  
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    Quote Originally Posted by JeromeONeill View Post
    Quote Originally Posted by Robittybob1 View Post
    Quote Originally Posted by JeromeONeill View Post
    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?
    Is the Neodymium magnet shaped like a bar magnet?
    Float the electromagnet on water and approach the neodymium magnet from various angles and see it the electromagnet rotates.
    The charger does that produce a continuous current or an alternating current? Or is it pulses of current" When there is no current the core of your magnet could be attractive to your neodymium magnet. What is the core made of?
    Yeah the neodymium magnet is cuboid shaped. I'm not sure what the type of current is being produced, I assumed it was a continuous D.C source seeing that it is for charging a car battery, that I'll have to look into . The core is made of a 4" steel nail. Ok thanks for the help I will try all that.
    Make the core out of non magnetic metal and see if that changes the picture. For then when the electromagnet is not working the neodymium won't have anything to attract to.
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  6. #5  
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    I'll try that
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  7. #6  
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    Quote Originally Posted by JeromeONeill View Post
    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?
    The magnetic field that your electromagnet is generating is unable to reverse the field caused by the external magnet. At the point at which it just cancels you will see zero attraction; beyond that you will get repulsion.
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    You are not bringing the neodymium magnet's poles close to the correct poles of the electromagnet. Both are very directional and you need to bring South Pole to South Pole to make them repel each other, or North Pole to North Pole. Keep playing with it until you find the right angle where they repel.

    Also voltage isn't as important to magnetism as current. What is the resistance you have in series with your solenoid (that is an alternative term for your "electromagnet")? If you don't think you have any, do you have a current meter you can put in series? We need to know that to understand how much magnetic field you are generating; we may also need to know the diameter, length, and number of turns of your solenoid depending on your exact setup.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by JeromeONeill View Post
    Hello I'm new to this forum and this is my first post.
    I have an electromagnet powered by a car battery charger set at 12 volts. The problem is the electromagnet won't repel the neodymium magnet however it is strong enough to pick up a wire strippers. I tried changing the polarity of the electromagnet by switching the leads going from the battery charger to the electromagnet, also I tried turning the magnet around so its other pole would be facing the electromagnet and I tried placing the magnet at the other end of the electromagnet. However nothing seems to works. So I'm wondering does anyone know what I'm doing wrong?
    The magnetic field that your electromagnet is generating is unable to reverse the field caused by the external magnet. At the point at which it just cancels you will see zero attraction; beyond that you will get repulsion.
    I like this answer too. For I can see that the electromagnet is going to have to be quite strong to overcome the initial attraction to the steel core.
    Have I got that right?
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    Quote Originally Posted by Robittybob1 View Post
    I like this answer too. For I can see that the electromagnet is going to have to be quite strong to overcome the initial attraction to the steel core. Have I got that right?
    Basically yes. You have two things going on here:

    1) There is some amount of attraction caused by the permanent magnet (which generates a static magnetic field) and the iron of the core of the electromagnet.

    2) There is some amount of repulsion caused by the magnetic field created by the solenoidal windings of the electromagnet per Ampere's Law. If this exceeds the attraction of case 1) the two will repel. If it does not, then no matter what the orientation, there will be some attraction between the two.
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    Quote Originally Posted by Schneibster View Post
    You are not bringing the neodymium magnet's poles close to the correct poles of the electromagnet. Both are very directional and you need to bring South Pole to South Pole to make them repel each other, or North Pole to North Pole. Keep playing with it until you find the right angle where they repel.Also voltage isn't as important to magnetism as current. What is the resistance you have in series with your solenoid (that is an alternative term for your "electromagnet")? If you don't think you have any, do you have a current meter you can put in series? We need to know that to understand how much magnetic field you are generating; we may also need to know the diameter, length, and number of turns of your solenoid depending on your exact setup.
    What's happening is that the neodymium magnet is over coming the field of the electro magnet so no matter what way I turn the magnet or which end of the electromagnet it is facing it gets attracted to the iron core
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    Quote Originally Posted by JeromeONeill View Post
    Quote Originally Posted by Schneibster View Post
    You are not bringing the neodymium magnet's poles close to the correct poles of the electromagnet. Both are very directional and you need to bring South Pole to South Pole to make them repel each other, or North Pole to North Pole. Keep playing with it until you find the right angle where they repel.Also voltage isn't as important to magnetism as current. What is the resistance you have in series with your solenoid (that is an alternative term for your "electromagnet")? If you don't think you have any, do you have a current meter you can put in series? We need to know that to understand how much magnetic field you are generating; we may also need to know the diameter, length, and number of turns of your solenoid depending on your exact setup.
    What's happening is that the neodymium magnet is over coming the field of the electro magnet so no matter what way I turn the magnet or which end of the electromagnet it is facing it gets attracted to the iron core
    Set it up with a non magnetic metal core.
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  13. #12  
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    Quote Originally Posted by Robittybob1 View Post
    Quote Originally Posted by JeromeONeill View Post
    Quote Originally Posted by Schneibster View Post
    You are not bringing the neodymium magnet's poles close to the correct poles of the electromagnet. Both are very directional and you need to bring South Pole to South Pole to make them repel each other, or North Pole to North Pole. Keep playing with it until you find the right angle where they repel.Also voltage isn't as important to magnetism as current. What is the resistance you have in series with your solenoid (that is an alternative term for your "electromagnet")? If you don't think you have any, do you have a current meter you can put in series? We need to know that to understand how much magnetic field you are generating; we may also need to know the diameter, length, and number of turns of your solenoid depending on your exact setup.
    What's happening is that the neodymium magnet is over coming the field of the electro magnet so no matter what way I turn the magnet or which end of the electromagnet it is facing it gets attracted to the iron core
    Set it up with a non magnetic metal core.
    The idea is that when the electromagnet is turned off the neodymium magnet will be attracted to the iron core and that when the electromagnet is turned on it should repel the neodymium magnet
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    Quote Originally Posted by JeromeONeill View Post
    Quote Originally Posted by Robittybob1 View Post
    Quote Originally Posted by JeromeONeill View Post
    Quote Originally Posted by Schneibster View Post
    You are not bringing the neodymium magnet's poles close to the correct poles of the electromagnet. Both are very directional and you need to bring South Pole to South Pole to make them repel each other, or North Pole to North Pole. Keep playing with it until you find the right angle where they repel.Also voltage isn't as important to magnetism as current. What is the resistance you have in series with your solenoid (that is an alternative term for your "electromagnet")? If you don't think you have any, do you have a current meter you can put in series? We need to know that to understand how much magnetic field you are generating; we may also need to know the diameter, length, and number of turns of your solenoid depending on your exact setup.
    What's happening is that the neodymium magnet is over coming the field of the electro magnet so no matter what way I turn the magnet or which end of the electromagnet it is facing it gets attracted to the iron core
    Set it up with a non magnetic metal core.
    The idea is that when the electromagnet is turned off the neodymium magnet will be attracted to the iron core and that when the electromagnet is turned on it should repel the neodymium magnet
    Well you have to put more current through the electromagnet or put more windings on the electromagnet.
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    Quote Originally Posted by JeromeONeill View Post
    The idea is that when the electromagnet is turned off the neodymium magnet will be attracted to the iron core and that when the electromagnet is turned on it should repel the neodymium magnet
    This is the problem with a purely qualitative approach. Yes, in the abstract, an electromagnet will generate a repulsive force. But here you have, as others have pointed out, more than just an electromagnet. You also have a magnetic core, and the permanent magnet exerts an attractive force on that. To figure out what will happen on the whole, you need to perform a calculation to see under what conditions repulsion will win over attraction, and whether your experimental conditions meet those requirements. It does not appear that you did any calculations at all, so you shouldn't be surprised that the experiment behaves as it does.

    A NIB magnet, by the way, generates a huge flux density, so you will find it challenging to generate suffcient flux density with your electromagnet to offset its attraction for the iron core. You'll need many, many ampere-turns to have a chance.
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