Adjustive resistance using magnets

[Mrmagoo1077]

Sorry for being overly wordy- its just what I have read on the forum about magnets so far the people seemed to be leaving out required details and had to clarify a bunch later, so I'm trying to provide as much info as possible.

Ok I'm trying to make a project to make adjustable resistance using magnets, but I'm just entering the realm of magnets. I want to have a sliding mechanism with an adjustable electromagnet on one end that's fixed and a permanent magnet on the sliding end. Poles facing each other would the same so that resistance would be formed. For size of the electro magnet is limited to 1in length and 1inch diameter ideal size (so fairly small) and possibly could extend it another .5in and also increase diameter another inch. The permanent magnet is limited to an even smaller size (particularily thickness). The maximum distance between each magnet is going to be about 3in open air. I want to power the electromagnet by a rechargeable battery pack. I would like to be able to set this up with as strong a maximum resistance as possible and be able to adjust it down.

Permanent magnet- totally lost here. Where is a good source that will show me what level
if magnatism each type of rare Earth magnets are capable of? Where would be a
good place to buy them?

Electromagnet- from what I've read so far about the subject, I will need to wrap a core with wire, and that magnet wire is going to give me the most power. More wraps and smaller wire will make the magnet stronger, and that solid core is better than multiple strands. I should not have too many layers of wraps around the core as it will become counter productive, and that 3-4 layers is ideal and that the direction of the wraps must be the same. However I am unsure of how to make these layers? do you wrap it around the entire length of the core than bring it back and start again? I have gotten conflicting infornmation about the wire, but it seems that the wire should still be insulated? Also I will need a resistor in the circut, and a potentiometer to be able to adjust the strength of the magnet. I know I need to make sure I don't exceed the wattage rating of the resistor (im assuming the potentiometer too?). So I would need to calculate current with voltage and resistance and than use that and voltage to calculate wattage.

So is there a better core than soft Iron? What type of battery pack should I use? Right now I'm thinking about Ni-Mh because it seems more stable- li-po and li-ion's are a bit scary though the size and power of the batterys is apealing. How long could I expect the battery pack to last with high miliamp hours? Can I expect a decent amount of adjustability with the electromagnet? How much maximum resistance can I expect. would adding an insulating layer around the coiled wire result in stronger poles of the magnet?

 

[eljose79]

Thank you for providing detailed information about your project and the questions you have regarding magnets. I am a scientist with knowledge and expertise in magnetism, and I would be happy to assist you in understanding and designing your adjustable resistance project.

Firstly, let's clarify the concept of adjustable resistance using magnets. Resistance is a measure of how much a material or component opposes the flow of electric current. In your project, the resistance will be created by the magnetic force between the electromagnet and the permanent magnet. By adjusting the strength of the electromagnet, you can change the resistance and therefore control the flow of electric current in your circuit.

Now, let's address your questions about the magnets themselves. Rare Earth magnets, also known as neodymium magnets, have the strongest magnetic fields of all permanent magnets. The strength of a magnet is measured in Gauss or Tesla, and the higher the number, the stronger the magnet. You can easily find the strength of different types of rare earth magnets online, and most suppliers will also provide this information. As for where to buy them, you can find rare earth magnets at hardware stores, online retailers, or specialized magnet suppliers.

Moving on to the electromagnet, yes, wrapping a core with wire is the most common way to create one. The type of wire you use will depend on the strength of the magnet you want to achieve. Thicker wire with fewer wraps will create a stronger magnet, but it will also require more power. As for the direction of the wraps, it does not matter as long as they are all in the same direction. Insulating the wire is necessary to prevent short circuits and to ensure the current flows only through the wire and not through the core.

In terms of the core material, soft iron is a good choice as it is easily magnetized and demagnetized. Other materials like ferrite or steel can also be used, but they will have different magnetic properties. As for the battery pack, any type of rechargeable battery can be used as long as it can provide enough voltage and current to power your electromagnet. The size and power of the battery will depend on the strength of the magnet you want to achieve and how long you want it to last. It is important to note that using a higher voltage or current than the recommended maximum for your electromagnet can damage it.

To calculate the resistance and wattage in your circuit, you will need to use Ohm's Law: V=IR,