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sarahjt1

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Ok... so there really isn't a homework problem that goes directly with what I am asking... I just want to understand how/why induction (magnet through a coil) gave certain results in our Science Workshop program...

Here is what we did in our lab:

We dropped a magnet (south end in first) through a coil hooked up to a voltage sensor and photogate to measure the area of our emf vs. time plot. We didn't do any calculations the computer did... but it used the concept of Faraday's law of induction. The resulting graph had a high point and a low point.

The high point's area beneath the curve was 0.021VoltSec

The low point's area above the curve was -0.020VoltSec

I understand that the area's have to be equal because Lenz's law states something to the effect that whatever change we've made we have to give back.

BUT What I don't fully understand is WHY it is a negative value? Is it because the current flow changes direction?

I don't fully understand the right hand rule either and I don't know exactly which direction the current was flowing as the south end of the magnet entered the coil... but I do know that it will reverse direction once the magnet is leaving the coil and that the point on the graph that y=0 (voltage) is the point when the current is reversing.

Basically, I want to conceptually understand the theory and how it is applied to the lab we did... here is the lab guide http://physics.unr.edu/152labs/Magnetic_Induction.pdf

Here is what we did in our lab:

We dropped a magnet (south end in first) through a coil hooked up to a voltage sensor and photogate to measure the area of our emf vs. time plot. We didn't do any calculations the computer did... but it used the concept of Faraday's law of induction. The resulting graph had a high point and a low point.

The high point's area beneath the curve was 0.021VoltSec

The low point's area above the curve was -0.020VoltSec

I understand that the area's have to be equal because Lenz's law states something to the effect that whatever change we've made we have to give back.

BUT What I don't fully understand is WHY it is a negative value? Is it because the current flow changes direction?

I don't fully understand the right hand rule either and I don't know exactly which direction the current was flowing as the south end of the magnet entered the coil... but I do know that it will reverse direction once the magnet is leaving the coil and that the point on the graph that y=0 (voltage) is the point when the current is reversing.

Basically, I want to conceptually understand the theory and how it is applied to the lab we did... here is the lab guide http://physics.unr.edu/152labs/Magnetic_Induction.pdf

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