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## Homework Statement

A current I flows to the right on the x-axis from the origin to x = infinity. What's the magnitude of the magnetic field at (x,y) = (0,L)?

## Homework Equations

B = u sub 0 time I/(2 pi R)

## The Attempt at a Solution

We use above equation since we have an extremely long wire. I would think I should just replace the R for the L as the given point value of y. However, this is an old exam question and the professor's solution states that B ' = 1/2 B and therefore the answer is:

u sub 0 times I / (4pi L) Could someone please explain why the statement of B' = 1/2 B makes sense. If I know that then of course the answer in the exam key would make perfect sense! Thanks for your time and effort, Frostking