# Confirming Faraday's Law - interference in measurement.

1. May 25, 2013

### peripatein

Hi,
1. The problem statement, all variables and given/known data
We ran an experiment for confirming the linearity of Faraday's Law (the relation between EMF and the rate of change of flux), by plugging a magnet to a motor rotating in the axis of a solenoid (inductor). In my graph of the amplitude of EMF wrt time, I noticed some disturbances on a few of the peaks. What might have been the causes of such interference("noise")?

2. Relevant equations

3. The attempt at a solution

2. May 25, 2013

### barryj

You might give some more details of your experiment. What do you mean by "plugging a magnet to a motor rotating in the axis of a solenoid (inductor)." Are you changing the speed of the motor or just plotting the emf vs time. How are you measuring the emf, a scope?

3. May 25, 2013

### peripatein

We were measuring the EMF produced as a result of the rotating magnet inside the solenoid, by changing the angular frequency of the rotation (the speed of the motor). Hence, for various frequencies we obtained various EMFs. I cannot tell for sure, I fear, whether the device used to measure the EMF was a scope.
Is it nevertheless clearer now? Could you assist?

4. May 25, 2013

### rude man

I agree with barryj, you need to describe the setup in detail. For example, the solenoid has inductance and a 'scope has capacitance, which might result in peaking somewhere. Etc.

5. May 25, 2013

### peripatein

I am not really sure how to provide more details than I already have. We might have indeed used a scope, and it's highly likely we did, but I couldn't vouch for that. Anything else?

6. May 25, 2013

### peripatein

I am merely interested in the possible, most probable causes for the interferences ("noises") shown in the graphs, as a means of explaining them.

7. May 25, 2013

### rude man

So how about showing us the data? We can't perform an autopsy without a body ...

8. May 25, 2013

### peripatein

Please see attachment. Y axis is EMF, X axis is time. I hope this will suffice :)

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9. May 25, 2013

### rude man

As a guess, I'd suspect motor vibrations. The noise is not random, that's for sure. And the "plugging" of the magnet into the motor, that connection might have some slop in it.

About the best I can do I'm afraid.