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A changing magnetic field induces electrical current in a wire and is the basis for electrical generation. Also an electrical current flowing through a wire creates a magnetic field and is the basis for most motors. In general a changing magnetic field creates an electrical field and a changing electrical field creates a magnetic field
Devilonline: Why is this relationship not perpetual?
It is perpetual...its never ending like if u dont disturb the magnetic field or electric current it wont stop like in motors and generators
it is indeed perpetual.. and thats where james clerk maxwell comes into play.. he saw that they would keep on doing it. and hence he defined his electromagnetic waves!!
Devilonline, how does this not violate conservation of energy?
Cause energy is not lost in the process!
I was implying that it was created. But, I'm assuming it's not so ... where is that additional energy obtained from?
see initially some energy is required to create a disturbance.. infact.. in order to get an electromagnetic wave you need to accelerate charges (oscillating charges).. thats what happens when you switch on your bulb... the filament is heated to a high temperature... which causes the atoms to vibrate and they produce these electromagnetic waves.. so after a while the light diminishes right?..
If you mean as in the light bulb dying then, yes.
No as in becoming dull a bit
exactly.. it dies off.. so the disturbance eventually dies off
No wait ur saying wen we turn on a bulb
Devilonline, are you talking to me or Mashy?
So then like it doesnt die off
Sorry i shud specify...mashy
all waves.. eventually die off right??.. a ripple in water.. doesn't keep on going continuously.. theoretically it should.. but in reality it doesn't.. thats what I am saying!
So the light doesnt diminish the waves do no?
Ok, what about reality prevents that ripple from continuing? Other ripples that cancel the wave out, etc? So, about an engine, are you saying it would get more and more powerful infinitely if the engine never broke?
Without giving it more energy.
the light DOES diminish... cause if you switch on teh bulb.. and you keep going farther and farther away.. the light becomes dull and finally at one point.. for all practical purposes you can't see the light at all!!
Ooohhh!! I get it!! :D
S3a same here i dnt get what u r saying
Sorry lol. Two secs.
"It is perpetual...its never ending like if u dont disturb the magnetic field or electric current it wont stop like in motors and generators " This implies that if I give a motor some energy, I will never need to give it any more since it will (perpetually) make it on its own so the motor should go on forever until it breaks but, this doesn't seem to be the case with cards. You need to keep burning fuel (or whatever) to feed energy. So what am I missing? Also, sorry for being difficult to understand. I am presently tired but this topic striked my curiosity.
That the more electromagnetic energy u need more elcectricity and a stronger magnet u would need otherwise it would have the same magnitude of power...in cars u press the accelerator and it accelerates by getting more power from the battery
Like if u need a constant EMF source
s3a.. you have friction.. if there was no friction.. then what you said is right!!
Mashy, friction with the car parts?
Oh yea eddy currents
No eddy currents....u know what they are??
I don't know what eddy currents are.
What I meant by "car parts" is basically "not tires".
Mashy the friction is cuz of the eddy currents right?
i mean we live in a world comprised of friction.. thats why we need to put in more energy.. !! if there was no friction.. then a car once set into motion.. will keep moving until it hits something :P.. and friction inside car parts, friction between tyres and roads.. even if there was only friction INSIDE car parts.. but not outside.. then also.. once car set in motoin
Mashy also because of eddy currents
Mashy, I didn't understand what you said about if there was friction only INSIDE.
Ok so the bottom line is, energy can be created perpetually but it is lost to friction so the end result is you need to put more energy in manually?
Rather than relying on the "perpetual"ness.
yea yea.. correct .
I think a better word would be "obtained" rather than "created". Would it?
For the energy.
Yesssss!!! I think i got confused about my concepts too by this question lol
Glad, I could do my part lol. :)
Wait which grade r u in s3a?
I already did my first electromagnetic course (before university). Right now, I'm going to 2nd year software engineering.
Non-university level by the way.
For the E&M course.
OMG and im explaining this to u lol no wonder i got confused by ur questions....ohbwait u did ur electromagnetic course but u dont know about eddy currents O.o
Maybe I just don't know them by name.
Did you learn that in the first year undergrad course (US system)?
Eddy currents (also called Foucault currents) are electric currents induced within conductors by a changing magnetic field in the conductor. These circulating eddies of current have inductance and thus induce magnetic fields. These fields can cause repulsive, attractive, propulsion, drag and heating effects. The stronger the applied magnetic field, or the greater the electrical conductivity of the conductor, or the faster the field changes, then the greater the currents that are developed and the greater the fields produced.
Nope olevels (cambridge system)
Well, I don't remember the stuff well and I need to review but is that like getting the intensity of the induced emf?
I don't know the UK system. Do you have a school before University and after High school?
What comes before senior year in highschool?
That just confused me more lol. In Canada, there is high school and then University but in Quebec there is high school --> CEGEP/College --> University
Do you have a middle school like that?
Again, I'm tired right now so sorry if I say stupid things.
No like ok ill make it simple im talking about the 11 and 12th grade
Well, I technically did it in 13th if I remember correctly and I did the waves course before instead of after.
waves, optics, modern physics
Oohk that makes sense now
Yea we do it in the 12th grade
Sorry i meant 11th
Oh, 11th I did kinematics, optics, stuff like that.
Lol nice working with u lol tc
You too. :) Bye.