Magnetism - Quick solenoid question

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AI Thread Summary
A user calculated the magnetic field B inside a 200-turn solenoid but initially arrived at an incorrect answer of 7.28x10^-5 T instead of the expected 0.3 mT. The user realized they mistakenly used the wrong current value from a different problem. After correcting the current to 0.29A, they were able to resolve the confusion. The discussion highlights the importance of using accurate values in calculations for magnetic fields in solenoids. Accurate input is crucial for obtaining the correct results in physics problems.
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Homework Statement


A 200-turn solenoid having a length of 25cm and a diameter of 10cm carries a current of 0.29A. Calculate the magnitude of the magnetic field B inside the solenoid.


Homework Equations


B = \mu0ni


The Attempt at a Solution


Well, I plugged the numbers into the equation and got 7.28x10^-5 T as the answer. However, this is wrong. The correct answer is meant to be 0.3 mT. I can't see where I've gone wrong because the magnetic field inside a solenoid is meant to be independent of its dimensions, right?

EDIT: I found the number of turns per unit length, then put that into the equation and still get the wrong answer. I'm confused.

B = 4\pix10-7 Tm/A x (200/0.25) x 7.5A = 7.28x10^-5.

I've no idea why I get that. Maybe the diameter has some significance that I haven't managed to see yet.
 
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Show exactly what you plugged in for each factor.
 
thehammer said:
A 200-turn solenoid having a length of 25cm and a diameter of 10cm carries a current of 0.29A.
...
B = 4\pix10-7 Tm/A x (200/0.25) x 7.5A = 7.28x10^-5.
Looks to me like you are using the wrong current.
 
Oops. I apologise for wasting time. I used a current from a different question by accident :).
 

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