# Inductor calculation

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#### hussam123

##### Newbie level 4
In magnetic circuit, How many turns are when a conductor winded around a square mild steel core with permeability ( Ur=2410) The outer length is 20 cm and inner length is 16 cm. the current measured is 1,482A. Length of the coil is 10cm
any Hint where to begin.

#### c_mitra

We need the cross sectional area of the core is needed.

The DC current cannot be used (ideal inductor has zero DC resistance)

The AC current need to be specified with frequency.

The problem cannot be solved with the given information.

#### frankrose

You need the shape of the cross-section, rounded or rectangle? It determines the area. The current is DC or AC? If DC what is the material of the turns, else how much is the frequency?

#### hussam123

##### Newbie level 4
these the only information provided in the question. The formula says H = I.N/I
where is H , magnetic field strength
I current in the coil
N , number of turns
I the length of the metal circuit

#### FvM

##### Super Moderator
Staff member
these the only information provided in the question. The formula says H = I*N/l
where is H , magnetic field strength
I current in the coil
N , number of turns
l the length of the metal circuit
The formula is correct, but how you relate H to µr given in the question? You also forgot to give the complete core dimensions. You gave x size, but y size is missing, thus we can't calculate magnetic path length l.

I wonder if it's a saturation problem. Soft steel initial and maximal µr is much higher than assumed 2400, if a µr versus H curve is given, one could determine a respective H value. In any case, something is missing.

#### hussam123

##### Newbie level 4
Let me backup.
I have 4 questions about magnetic.
The first question is to find the field strength distance of a a straight conductor , 0,48 cm from the conductor. Current is 3 Ampere.
Question number two is to find how many turns in the drawing for the giving information. only given are Current, relative permeability , and length of the coil, the cross section is square. Outer and inner length are given.
I have a similar example in the book where they applied the formula A=B.D .
A is the cross section in m^2
B outer length
D inner length
then they applied HOPKINSON'S law, Ampere winding number Fm=I.N and the formula Reluctance in a circuit Rm= Iota( greek letter) / u.A

#### c_mitra

these the only information provided in the question. The formula says H = I.N/I

You are right; the flux density is directly proportional to the ampere-turns per unit length. You will need the cross sectional area to calculate the total flux.

B and H are independent of the area (they are field strengths) and are related to the flux density (and not the total flux).

Now the current and the length of the solenoid are given, you need to know the desired field to determine the number of turns.

#### hussam123

##### Newbie level 4
This is my work

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