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Re: electromagnetism

this (at least upon a quick reading) is a simple plug in the formulae question.
I suggest you visit (again) your library, as you're not getting much co-operation
from us. [This was permitted (even encouraged) when I took take home exams at
UCSB.]

hint: Harnwell has a section on the magnetic circuit and another on the iron
core transformer. I checked Bleaney and Bleaney -- has one page on MMF,
reluctance, etc.

bc

P.s. I see I miss-read you post, as did Ludwik. If you still can't find a worked
e.g., I may help you. However, this is sucha common problem, I am surprised you
haven't found help in your text or another in the library. (Reitz and Milford
also discuss this problem.)

Ludwik Kowalski wrote:

Suppose I do remember how to solve such problems (I do not)
and post a solution. Would you present it to your teacher as
your own or would you give me credit for doing this for you?
Ludwik Kowalski

paul giusti wrote:

i am from Hamilton, near Glasgow and am at Strathclyde Uni doing Electronic
and Electrical Engineering. i have an exam on electromagnetism when i return
from my holidays,hence why i cannot get in contact with my lecturers. i have
been doing past papers, however i do not have any worked solutions. the
question i have put on this e-mail is one that has appeared in previous
exams however i cannot seem to do it or find anything in any books or my
notes to help me. sending the question to physics lecturers is my only hope.

thanks in advance

kind regards
paul

a transformer is constructed from E- and I-shaped cores with coils wound
around the center limb. the middle part of the core has length 25mm and
cross-sectional area 160mm^2, with a mean flux path length of 50mm on each
side.

The relative permeability of the core is 1200. the primary coil has 400
turns, while the secondary has 100 turns.

a) calculate the total reluctance, and the self-inductance of the primary.

b) if 240 V is applied to the primary and a load of 50ohms is connected
across the secondary, determine the flux and flux density in each limb of
the transformer.

c) determine the percentage drop in the flux through the centre limb if a
manufacturing fault leaves a 0.1mm gap between it and the I plate.

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