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Home > Archive > Electrical Engineering > February 2008 > Electric Motors
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| Harish 2008-02-16, 9:25 pm |
| Hi,
I am taking a course on electric motors and i have a couple of
questions.
1) When you have a wire and you loop it through an iron bar, what
causes the iron bar to become a magnet?
2) What does induced emf mean?
Thanks
Harish
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| gfretwell@aol.com 2008-02-17, 3:25 am |
| On Sat, 16 Feb 2008 18:52:08 -0800 (PST), Harish
<mahadevan.swamy@gmail.com> wrote:
>1) When you have a wire and you loop it through an iron bar, what
>causes the iron bar to become a magnet?
When you pass current through a wire it generates a magnetic field,
winding the wire around an iron core makes that field add up 1x per
turn
>2) What does induced emf mean?
When you stop passing current through that wire the field you built up
collapses and gives that energy back to the wire, usually very quickly
with a "spike" in the voltage. That is how the spark coil works in a
car.
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| Gerald Newton 2008-02-17, 3:25 am |
| On Feb 16, 5:52=A0pm, Harish <mahadevan.sw...@gmail.com> wrote:
> Hi,
>
> I am taking a course on electric motors and i have a couple of
> questions.
>
> 1) When you have a wire and you loop it through an iron bar, what
> causes the iron bar to become a magnet?
> 2) What does induced emf mean?
>
> Thanks
>
> Harish
Try:
http://www.allaboutcircuits.com/vol_2/chpt_10/4.html
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|
> 1) When you have a wire and you loop it through an iron bar, what
> causes the iron bar to become a magnet?
> 2) What does induced emf mean?
read a textbook. if u don't understand something specific in the
textbook, try asking ur friends on the course...or your teacher.
there's loads on the web. if ALL else fails post the question here.
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| From: mahadevan.swamy@gmail.com (Harish)
Hi,
I am taking a course on electric motors and i have a couple of
questions.
1) When you have a wire and you loop it through an iron bar, what causes
the iron bar to become a magnet?
2) What does induced emf mean?
Thanks
Harish
--------------------
1) At an atomic level the atoms in the iron bar are aligned + to - and
thus acquire magnetic properties.
2) An Induced emf is a voltage source implied on a conductor by another
conductor - as in a transformer - the primary coil holds the applied emf
and the secondary coil holds the induced emf - which can be lesser or
greater than the applied emf depending on the turns ratio with respect
to the turns on the primary coil....
Read and study the diagrams & pictorials.
Roy Q.T. ~ US/NCU ~ E.E. Technician
[have tools, will travel]
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| Don Kelly 2008-02-19, 8:25 pm |
| ----------------------------
"Roy" <ROYKEY@webtv.net> wrote in message
news:21472-47BB5978-1207@storefull-3252.bay.webtv.net...
> From: mahadevan.swamy@gmail.com (Harish)
> Hi,
> I am taking a course on electric motors and i have a couple of
> questions.
>
> 1) When you have a wire and you loop it through an iron bar, what causes
> the iron bar to become a magnet?
>
> 2) What does induced emf mean?
> Thanks
> Harish
> --------------------
> 1) At an atomic level the atoms in the iron bar are aligned + to - and
> thus acquire magnetic properties.
>
> 2) An Induced emf is a voltage source implied on a conductor by another
> conductor - as in a transformer - the primary coil holds the applied emf
> and the secondary coil holds the induced emf - which can be lesser or
> greater than the applied emf depending on the turns ratio with respect
> to the turns on the primary coil....
>
> Read and study the diagrams & pictorials.
>
> Roy Q.T. ~ US/NCU ~ E.E. Technician
> [have tools, will travel]
>
---------
Comment :
An induced voltage is caused by a changing magnetic field enclosed by the
conductor.
This magnetic field may be produced by a permanent magnet or a DC current
with relative motion involved- or by a changing current in either the
original or another conductor.
Strictly speaking an emf in one coil does not produce induced emf in
another coil, The relationships between emfs in an ideal transformer are due
to the fact that magnetic flux is common to both windings.
For example: The voltage induced in a DC motor is produced by relative
motion between the armature coils and the stator field and has nothing to do
with the stator field winding emf but a great deal to do with the stator
field current.
Don Kelly dhky@shawcross.ca
remove the X to answer
| |
|
| So, what else is there ? I would pretend to not know the fact that there
are several methods of inducing an emf...
This guy should do his homework instead of asking for a quick response.,
if things haven't changed [& they haven't] the only correct answer is
the one the teacher chosen or wants to hear, purely based on what ever
text book or previous lesson he may have given or assigned.
=AE
| |
| Don Kelly 2008-02-20, 9:25 pm |
| ----------------------------
"Roy" <ROYKEY@webtv.net> wrote in message
news:15925-47BBBAE2-1054@storefull-3253.bay.webtv.net...
So, what else is there ? I would pretend to not know the fact that there
are several methods of inducing an emf...
This guy should do his homework instead of asking for a quick response.,
if things haven't changed [& they haven't] the only correct answer is
the one the teacher chosen or wants to hear, purely based on what ever
text book or previous lesson he may have given or assigned.
-----------------------------------------
Agreed that he should have done his homework. Disagree on the "only correct
answer" comment except that sometimes the question is intended to emphasise
a certain aspect for a specific reason at that time. This does not mean that
one should bury one's head in the sand and try a one size fits all and use a
formula without any understanding of its basis and limitations eve if it is
easier than thinking.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
| |
|
| From: dhky@shaw.ca (Don=A0Kelly)
----------------------------
"Roy"
wrote a in message:
So, what else is there ? I would pretend to not know the fact that there
are several methods of inducing an emf...
This guy should do his homework instead of asking for a quick response.,
if things haven't changed [& they haven't] the only correct answer is
the one the teacher chosen or wants to hear, purely based on what ever
text book or previous lesson he may have given or assigned.
-----------------------------------------
Agreed that he should have done his homework. Disagree on the "only
correct answer" comment except that sometimes the question is intended
to emphasise a certain aspect for a specific reason at that time. This
does not mean that one should bury one's head in the sand and try a one
size fits all and use a formula without any understanding of its basis
and limitations eve if it is easier than thinking.
--------------------
Disagree???
Lets say an orange is yellow & round, both assertions are correct but if
shapes are being discussed there is only one correct or appropriate
answer., and in the OPs case that would be determined by what was
previously discussed in class, of which we know nothing......For the
sake of ones grades it's best to stay focused on the classes course -
and leave creativity & open minded discussion for the work
force......that is not burying ones head in the sand., just keeping ones
nose out of the garbage.
Roy Q.T. ~ US/NCU ~ E.E. Technician
[have tools, will travel]
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