Calculating Flux Density and Induced Voltage in a Linear Induction Flashlight

[radaballer]

For my science fair i am attempting to make a linear induction flashlight. I am a bit confused on how to demonstrate the scientific effects mathematically. I would greatly appreciate any help. Farradays law states
EMF= -N(change in flux/ change in time). I am confused about how to find the change in flux. I have found the magnetic field to be 1006.842 Gauss at one inches away from the AXIS. Can i plug this figure into faraday's equation with respect to my design below? My concern is that the flux density at the axis will not accurately reflect the flux density which acts upon the the coil, which is not perpendicular to the axis. If i am correct, the induced voltage is contingent on the the field lines perpendicular to the direction of the current. Also, how do i demonstrate the implication of the magnets speed when shaken on the induced voltage ? Any contributions are appreciated.

 

[Khashishi]

You need better information about the field of your magnet. Make more measurements of the magnet until you can construct the 3D magnetic field from the magnet. You can probably treat the bar magnet as being comprised of two magnetic monopoles (this is only a mathematical trick; monopoles [probably] don't exist), so all you need to fully define the field is distance between monopoles and strength of each monopole.

 

[radaballer]

Ok thanks Is there a configuration program for this? Also, how is the speed of the magnet related to the induced current? Is there a formula for this? Also, say i make a 3d diagram of the mag field, how do i know which field lines will induce current?

 

[Khashishi]

You already wrote the formula up above. What you need to do is calculate the rate of change in the flux, which isn't so easy, but should be doable with a bit of vector calculus. How much mathematics do you know?

 

[radaballer]

Not enough to do that haha, but i will figure it out. Where do i start with solving this?

You already wrote the formula up above. What you need to do is calculate the rate of change in the flux, which isn't so easy, but should be doable with a bit of vector calculus. How much mathematics do you know?

 

[Khashishi]

I have no problem solving this, but I can't give you all the answers. You can simplify the problem a lot by making some approximations. If you represent the bar magnet by two magnetic monopoles (go read up on how to do this), the flux is fairly simple. You can use Gauss's law to calculate the flux from each magnetic monopole through each loop. How much solid angle does each loop subtend? The total flux is the sum of the flux from each monopole, thanks to the superposition principle. Then let the bar magnet move, and calculate the rate of change.