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Phy 122

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Divided by area

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Problem set 4 #1 states:

A straight wire segment of length 5.1 meters carries a current of 5.1 Amps. Find the strength of the magnetic field at a point lying 4.7 meters from the segment, if the segment is perpendicular to a vector from the center of the segment to the point.

Solution

The magnetic field at a point P due to a short current segment, with point P lying 'at a perpendicular' to the segment, is proportional to the current and the length of the segment.

Here a segment is 'short' if the field is measured at a distance large with respect to the length of the segment.

P lies nearly 'at a perpendicular' to the segment if a vector from the segment to P is at nearly a right angle.

The specific value of the magnetic field is given by B=k ' (IL)/r ^ 2.

In this situation we have I = 5.1 Amps, L= .059 m, and r= 4.7 meters.

Thus

IL= .3009 Amp meters, and

B = .0000001 Tesla / Amp meter)( .3009 Amp m)/( 4.7 m) ^ 2 = 1.362E-09 Tesla.

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When I work through this I end up with the units being Tesla/m^2

Do we drop the /m^2 because that's just understood?

Would it be correct to include that /m^2 (since for my own process I like to keep all the units in place to make sure I've included all the steps)?

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Thanks

@&

The unit of k ' is Tesla * meter / amp.

Technically this is the same as Tesla / amp meter, since by order of operations only Tesla would be divided by amp, with the result then multiplied by meters. However I suspect that I wrote the units carelessly.

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question form

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Phy 122

Your 'question form' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

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Final

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I see the finals week for VHCC ending 5/9.

I plan to take Test 4 no later than 5/8

I just want to make sure I'm reading the calendar correctly. Will this work?

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@&

That will work. I won't actually report grades until that weekend, so as long as I get the test by sometime on the 10th everything will be fine.

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