What is the inductance of a solenoid with a soft iron core?

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SUMMARY

The inductance of a solenoid with a soft iron core, consisting of 140 turns and a magnetic permeability of 750 μ0, is calculated using the formula L = (μN²A)/length. The correct calculation involves using the area A = π*(0.005m)² and the permeability μ = 750 * 4π * 10^-7 N/A². The final inductance value is 1.15E3 Henry, which converts to 1.15E6 milli-Henry. The discussion highlights the importance of correctly applying the permeability constant and avoiding arithmetic errors.

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  • Familiarity with magnetic permeability and its units
  • Knowledge of basic geometry for area calculations
  • Ability to perform unit conversions, particularly between Henry and milli-Henry
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  • Study the derivation of the inductance formula for solenoids
  • Learn about the properties of soft iron cores and their impact on inductance
  • Explore the significance of magnetic permeability in electromagnetic applications
  • Investigate common errors in inductance calculations and how to avoid them
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Physics students, electrical engineers, and anyone involved in designing or analyzing electromagnetic components, particularly solenoids and inductors.

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A solenoid has 140 turns uniformly wrapped around a soft iron core, which has a magnetic permeability =750 Uo (mue sub-knot) diameter of 10.0m and a length of 9.00cm.

What is the inductance in milli-henry (mH)?

Did I set this up right? Using L=(uN^2A)/length, you get:

(750*140^2*pi.005m^2*.09m)/.09m = 1.15E3 Henry = 1.15E6 Milli-Henry

I think I made a conversion error somewhere. If not, why would they ask for the inductance in milli-henry, and not kilo-henry? :confused:
 
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Your formula for L is correct. In your arithmetic I see two errors: an extra 0.09m on top, and--most importantly--a missing μ0. The permeability is μ = 750 μ0; μ0 = 4π10-7 N/A2.
 
ohhhhhhhhhhh! Thanks!
 

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