For a long solenoid, when the formula describes solenoid length, is it referring to the length of the wire wrapped around the magnetic core or the length of the core?
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2 Answers
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By "length of the solenoid," the formula is referring to the height or width of the solenoid, not the length of the wire. Refer to this diagram below:
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No, it refers to the height of the (hypothetical) cylinder around which the solenoid is wrapped.
Since this is a homework type question, I will provide hints to derive the formula:
- What is the magnetic field inside the solenoid with total $N$ turns, height $l$, carrying current $I$?
- If the number of turns is $N$ and cross sectional area is $A$, what is the magnetic flux $\phi$ through the solenoid due to its own magnetic field? (that will be $N$ times the flux through one turn)
- Finally, what is self inductance in terms of $\phi$ and $I$?
answered Jul 14, 2020 at 5:14