# Help With My Science Fair

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1. Sep 30, 2014

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.

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2. Sep 30, 2014

### 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.

3. Sep 30, 2014

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?

Last edited: Sep 30, 2014
4. Sep 30, 2014

### 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?

5. Sep 30, 2014