(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A long straight wire lies on a horizontal table and carries a current of 1.09 μA. A proton moves parallel to the wire (opposite the current) with a constant velocity of 12200 m/s at a distance d above the wire. The acceleration of gravity is 9.8 m/s2.

Determine this distance of d. You may ignore the magnetic field due to the Earth. Answer in units of cm.

2. Relevant equations

F = mg

F = qvB

B = (mu)* I / (2pi*r)

3. The attempt at a solution

I set mg = qvB and I solved for B.

After I found B, I plugged B into the equation B = (mu)* I / (2pi*r) to find r which I assume to be the distance that the question is asking for.

Here are the numbers I worked with:

(1.67e-27 kg) (9.81 m/s^2) = (1.602e-19 C)(12200 m/s) * (B)

B = 8.38e-12

To find r,

8.38 e-12 = [(4pi e-7)*(1.09e-6)] / [2pi * r]

I solved for r and found it to be 25.67 cm but this isn't the right answer. Could someone tell me what I did wrong?

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# Homework Help: Long Straight Wire & Proton

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