Calculating the magnetic field in solenoid

AI Thread Summary
When calculating the magnetic field in a solenoid, the formula B = μnI applies, where n is the turn density defined as N/L. The discussion centers on whether L should be the length of the solenoid or the mean length of the core when using a steel core with a small wrapped coil. It is clarified that L should refer to the length of the core surrounded by the coil, as the magnetic flux through the core is not affected by the turn density. This distinction is crucial for accurate calculations of the magnetic field. The consensus is that using the length of the core is the correct approach.
rp8308
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Just need a question cleared up.

If I had a coil wrapped around a core, and I was calculating the magnetic field of the solenoid using

B = μnI

where n = N/L, I is current and μ is the permeability of my material

N being the number of turns in the coil, and L being the length of the solenoid if there was an air core. Now if I had a steel core, for example, and the core was a large circular shape such that the coil itself only wrapped around a small amount of the core. Would the length L be the length of the solenoid still? (because its defined as turn density) or would it be the length that the magnetic flux takes through the whole core and therefore be the mean length of the core? (much larger than the length of the solenoid).

Cheers
 
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ok I am pretty sure its the length of core because flux through the core won't change with the density of turns, but could do with someone just confirming this... I hate when i confuse myself
 
Last edited:
If you meant to say L is the length of the coil, then yes I agree.

Edit: By 'length of the coil' I mean the length of the core which is surrounded by coil. (Not the actual length of the coil which is wrapping around it).
 

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