A very simple question

[bgarvin01]

Hi there, im doing an doing a question from a tutorial sheet in power engineering, here is the question: (im not looking the answer to the question)

 

A ferromagnetic core has mean path length

 

l1 of 50 cm. There is a small gap of 0.1cm in the structure

of the otherwise whole core. The cross-sectional area of the core is 15 cm

 

2, the relative permeability of

the core is 4000 and the coil of wire on the core has 500 turns. Find:

(1) the total reluctance of the flux path (iron plus air gap), and

(2) the current required to produce a flux density of 0.6 T in the air gap.

 

What I am unsure about is the when i look at the solution to the question I understand the formula but not why the cross sectional area of the core is written to be 0.0015m^2 or 15 x 10^-4. I say this as would it not be written as 0.15m^2 or 15 x 10^-2, could you explain why?

Aprreciate your help,

 

Ben

[imatfaal]

how many square centimetres in a square metre? You cannot convert square units using the same factor as linear units (nor volumetric units)

 

1 square metre measures 100 cm on each side!

[decraig]

...The cross-sectional area of the core is 15 cm...

 

Something is wrong with the problem statement, or your rendition.

 

It could be either (15 cm)^2, or 15 cm^2.

 

In practical design a ~3.9 cm x 3.9 cm core crosssection would have magnetic pathlength of about 36 cm, in my estimation for an E-I core. You might have better luck in the Engineering folder of this forum.

Edited November 26, 2013 by decraig