Calculation of Eddy Current Brake Force with a twist

[SwatiAnshu]

Homework Statement

I am carrying out an experiment which involves passing a magnet down a metal rod. This metal rod is placed at a certain angle. Throughout the experiment, I will keep changing the type of metal and the angle. Is there a certain formula that I can use to calculate the braking force?

Relevant Equations

Is there a formula through which I can use the angle, time taken to pass through rod etc.? Would appreciate any and all help! Thank you:)

All the equations I have seen have a component that is unknown. Also, if possible do let me know if there is a software I can use to model or analyze data related to eddy currents

 

[Merlin3189]

I don't know of any formula specifically for this situation.

What I suggest you might do is to get experimental data and see if you can deduce some empirical rules.

There should be a good relationship between the type of metal and speed, if the dimensions are the same.
If the dimensions vary, it might be difficult to sort out the factors.
If you have a range of sizes of one metal, perhaps you could work out that relation first.
What property of the metal do you think is important?

As far as the angle of tilt goes, there might be a problem with friction not being consistent. But you could try it and maybe the results would be consistent for some range of angles.

What factors do you think affect the breaking force? Or alternatively, the speed of fall?
Have you watched such an experiment? What does it tell you about the breaking force? (even without making any measurements.)

I hope you've already Googled this. Other people have tried all sorts of things. You could get some good ideas from them.

If you have any more info about your equipment / experimental set up, please show / tell us about it.

 

[SwatiAnshu]

I don't know of any formula specifically for this situation.

What I suggest you might do is to get experimental data and see if you can deduce some empirical rules.

There should be a good relationship between the type of metal and speed, if the dimensions are the same.
If the dimensions vary, it might be difficult to sort out the factors.
If you have a range of sizes of one metal, perhaps you could work out that relation first.
What property of the metal do you think is important?

As far as the angle of tilt goes, there might be a problem with friction not being consistent. But you could try it and maybe the results would be consistent for some range of angles.

What factors do you think affect the breaking force? Or alternatively, the speed of fall?
Have you watched such an experiment? What does it tell you about the breaking force? (even without making any measurements.)

I hope you've already Googled this. Other people have tried all sorts of things. You could get some good ideas from them.

If you have any more info about your equipment / experimental set up, please show / tell us about it.

Thank you for your response. I really appreciate it.
I have progressed further for my project.
I would like your opinion on the following: -

Would analysing the data I collected (time, angle and current) and plotting a relationship between velocity of the magnet and current induced help me justify a connection to eddy currents?

If it helps, I have attached a link to the raw data collected - apologies, it is not organised very well.

 

[Merlin3189]

Thanks for the new info.
Can you explain a bit more about your experiment?
I don't understand what current you are measuring.
Eddy currents are usually internal to the metal and may be different in different parts of the metal.
If you measured the longitudinal current induced in the rod, I wouldn't expect any. The movement would be parallel to the measured current, whereas induced currents are perpendicular to the motion.

I presume the angles are with respect tothe horizontal, so that 90 deg is falling vertically ?

In your first post you said metal "rod". I wondered if this was used with a torroidal magnet, or whether you actually used a metal tube with a solid cylindrical magnet? If it's a rod, doesn't an ordinary solid magnet just fall off a sloping rod? Or perhaps you are using a flat sheet of material and it slides on the surface?

 

[SwatiAnshu]

1. The current is measured across a coil that is around the metal rod itself.

2. Yes, the angles are with respect to the horizontal
3. The rod itself is hollow - hence a cylindrical neodymium magnet was passed through the rod.

Hope this makes it clearer and thank you for the help:)

 

[Merlin3189]

Yes, much clearer. You still need to say what the dimensions of each tube are.

I can see how you get a current now, though I'm not certain what it tells you. It explains the two readings +ve and -ve : do you understand why you get this?

I thought I could see a reason for a difference between the metals, but you also get a difference between the two copper pipes. Maybe the copper pipes differ not only in length, but also in diameter or thickness?

Are all the pipes the same diameter and thickness?

Do you use exactly the same coil of copper wire in every test?

If you have several things varying, it makes comparisons difficult.

Thinking about the currents: if the coil is the same and the magnet is the same each time, what could cause the difference in current? (If you say the type of metal, can you say why or how that would affect the current in the coil?)

I'm struggling a bit to make sense of your data. For eg. there is an entry highlighted for time of fall at 80 deg with the short copper pipe. This seems not to be the average of the relevant set of measurements. Maybe that's why this part of the table does not make sense to me?
I was pleased to see you marked the current in mA, but a lot of your other data entries are not clearly labelled. Obviously, as you say, this is just your rough work. It might make more sense when better presented.

I'm logging off now, but I'll look at any more posts tomorrow.