- #1

TDean2010

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## Homework Statement

"A solenoid is wound with 400 turns on a form 4cm in diameter and 50 cm long. The windings carry a current that produces a magnetic field, of magnitude 1.5mT, at the center of the solenoid. The magnetic flux through the solenoid is closest to?

## Homework Equations

L=N[itex]\Phi[/itex]/I

L=u

_{0}N

^{2}A/l

B-u

_{0}(N/l)I

## The Attempt at a Solution

So I calculated the current and inductance using the last 2 equations, getting I=1.492A and L = 5.05x10^-4

Then plugging that stuff into the self inductance equation and solving for magnetic flux I got 1.9x10^-6 Txm^2. But the answer my teacher gave in the solution key was 7.5x10^-4 Txm^2. I understand the difference between these two answers is having N=400 or not dividing by N at all when solving for magnetic flux, but I don't get why. I thought it would be 7.5x10^-4 if he had been asking for the flux in one turn (N=1), not the whole thing.

Is there something I am not reading in the question correctly that is making me think [itex]\Phi[/itex] = LI/N and using N=400 is correct? That is, can someone explain to me why the answer is 7.5x10^-4 snf noy 1.9x106-6?

Thank you very much!