coil

[yasir_ali]

Hey! every one.
I am newbie and even new to Electronics. These days i am studying Inductors. so i have read all the theory today morning. after reading the theory i was believing that there would be no magnetic field around coil, if i connect it to the D.C power supply. but when i just did that, the iron nail (used as core in coil) became magnetized. i am not understanding why the coil creates magnetic field with D.C supply? what i was think is that, with D.C supply at first, there would be some inductance as the current grows up. but when current reaches to its steady state and becomes constant then there would be NO Inductance so NO magnetic field should be there But..........
So please can some one make me understand this.

thanks

 

[transistor495]

Who told it I forgot actually. The primary theorem behind an electric motor is:

" There will be a magnetic field associated with a conductor which has an electricity flowing through it regardless of AC or DC.." -something like that I re-arranged as my theorem

If you consider a wire carrying DC through it, it has a magnetic field surrounding it...so the iron nail having a number of turns of wire around it -has a sum of all these magnetic fields -if you increase the turns, you'll increase the magnetic effect, also increase the current to achieve the same.

 

[ericgibbs]

Hey! every one.
I am newbie and even new to Electronics. These days i am studying Inductors. so i have read all the theory today morning. after reading the theory i was believing that there would be no magnetic field around coil, if i connect it to the D.C power supply. but when i just did that, the iron nail (used as core in coil) became magnetized. i am not understanding why the coil creates magnetic field with D.C supply? what i was think is that, with D.C supply at first, there would be some inductance as the current grows up. but when current reaches to its steady state and becomes constant then there would be NO Inductance so NO magnetic field should be there But..........
So please can some one make me understand this.

thanks

hi,
Inductance is determined by the number of coils and the material upon which the coil is wound, not the current flowing thru it, the inductance is always there.

Google: Flemings Rule and Lenzs Law for explanation.

 

[yasir_ali]

Can i say that with D.C power supply Inductance is ZERO? and yeah! i remind that the magnetic field is around any wire which carrying current (A.C or D.C). and you all know that, both the coils of the Transformers are connected by magnetic field. so why the transformers only work on A.C. we can have the same condition that if we connect one coil with D.C supply and magnetic flux will be developed around the primary coil and then this flux will cut the the turns in secondary coil. wouldn't it work? i know the answer for this is NO. because i did this experiment too. BUT why D.c cannot induce emf in secondary? only is it the reason that it does not reverse its polarity? is it the reason?

 

[ericgibbs]

Can i say that with D.C power supply Inductance is ZERO? and yeah! i remind that the magnetic field is around any wire which carrying current (A.C or D.C). and you all know that, both the coils of the Transformers are connected by magnetic field. so why the transformers only work on A.C. we can have the same condition that if we connect one coil with D.C supply and magnetic flux will be developed around the primary coil and then this flux will cut the the turns in secondary coil. wouldn't it work? i know the answer for this is NO. because i did this experiment too. BUT why D.c cannot induce emf in secondary? only is it the reason that it does not reverse its polarity? is it the reason?

No, that would be incorrect.

The reason why transformers work on AC is because the direction of the magnetic field linking the primary and secondary windings is changing direction, Alternating Current.

If you touch a battery on the primary winding of the transformer it will produce a voltage across the secondary for a few milli seconds, then it will fall to zero.

 

[transistor495]

Hi,
Because when AC is feeded through a transformer it has got a varying magnetic flux around primary-, ie, the direction of the magnetic field varies because of the negative and positive half cycles of AC, -that(flux) cuts the secondary winding and induces voltage on it.

The magnetic flux associated with a coil which has a DC passing through it -does not vary. So it will cut the secondary only when the powersupply is interrupted. It is possible if it is a switched DC.

I think I'm very slow..

 

[yasir_ali]

Yes! i've got it that every conductor has some inductance even a straight wire has some inductance but it only react with A.C (change in current) signal. am i correct? every wire has some inductance even connected with A.C or D.c it only react with A.c. i think i am right.

an inductor connected to A.c will react with A.c signal but the same inductor connect with the D.c signal will not react. Am i totally correct?