First off, I just want to say thank you for any help! Also, I ask that if you can, please try your best to explain this to me in layman terms. I understand ohm’s law and I have a decent grasp on electricity, so I don’t need water analogies. But I’m not very smart and i just love to learn how things work without really complicated equations. I don’t mean to sound demanding; i’m just requesting this sort “dumbed down” answer.

I have researched the internet for hours trying to understand this. I’ve heard time and time again that the magnetic field of an inductor and transformer are directly related to the amount of current in amps (obviously there’s the number of turns, surface area, core, etc.. as well, but I’m talking electrically). They also say that increasing voltage (assuming resistance stays the same) will increase current, and that’s the only reason that voltage would help supply the magnetic field with energy (or magnetic flux).

So here’s the thing. That doesn’t make sense to me. Why? Well for one, if you have 5 volts dc connected to a 5ohm circuit (setting aside an inductor’s initial impedance) , 1 amp of current flows. Now, if you have 20 bolts and 20 ohms, 1 amp flows. This means that in scenario 1, there are 5 watts of power. In scenario 2, there are 20 watts of power. So when an inductor initially charges up, there’s a high voltage drop across it..so unless that potential is being wasted, it must be giving power to the inductor.

Next, in an IDEAL transformer, if you have 1000V with up to 10A current in the primary, then step it down to 100V at up to 100A in the secondary, this means that it’s not just the current flow in amps that allowed the magnetic field from coil 1 to coil 2 to produce this power. Why? Because obviously the power, which is voltage x current, was saved on the second coil. So how then, could the magnetic field only be related to the amps of current and not the voltage (or maybe kinetic energy of the electrons if that’s what voltage “turns into”)?

If anyone could help me, again, I’d be really appreciative. Im not the best at explaining my questions sometimes, so if you need any clarification, please ask me.

Sorry for the long post. I didn’t mean for it to be this long.


1 Answer 1


First I will try to answer your second question. A transformer consists of one solenoid producing a magnetic field that affects a second solenoid. The magnetic field produced in a large solenoid is calculated from: $$B=\mu_0IN/L$$ where $\mu_0$ is the permeability constant, $I$ is current, $N$ is the number of turns and $L$ is the length of the solenoid. As you can see, it depends only on the current, because the magnetic field according to Maxwell's laws is caused by the movement of changes, not by the potential in which those charges are.

The process is much more complex than it seems. The current of the primary coil generates a magnetic field, which generates a voltage in the second coil (due to Maxwell's laws, and yes it seems confusing), as I have just said. This voltage divided by the resistance of the second coil will give you the current of the second coil. The difficulty comes when you find that the current of the primary coil depends on the resistance of the first coil, the resistance of the second coil, the inductance of both coils, the voltage applied to the first coil, and you will get a time-depending current. Why this dependence? Because the magnetic fields act like very weird resistors. Apart from that, the problem would be even more complex as there is a magnetic field caused by the secondary coil, but I won't go into that.

About the inductor (your first question, I think), I am not sure I have understood it correctly but you have to consider the inductor when calculating the current of a circuit as Ohm's law has to be modified. You don't have that $V=RI$ anymore, but that $V=RI-L\frac{dI}{dt}$ being L the inductance, which depends on the number of turns of the inductor, its area, etc. You will find that this means that there the voltage drop is caused both by the resistor and by the inductor.

  • $\begingroup$ Thanks for your reply. You say that with a transformer, the magnetic field and power induced in the second coil is only due to #1 coil current. But how does that make sense for power lines with thousands of volts with low current? Then that low current in the primary coil could induce a high current in the second coil. If you have 1000V at 10A being converted to 100V at 100A, that would mean that 10A is inducing 100A in the second coil. I don’t understand that. If voltage has nothing to do with it, then I’m baffled. I’d really appreciate if you would elaborate on that for me! Thanks again! $\endgroup$ Commented Apr 9, 2022 at 21:35
  • $\begingroup$ I have updated my answer, I hope it helps $\endgroup$ Commented Apr 9, 2022 at 22:19
  • $\begingroup$ Thank you very much for taking the time to help me. I sort of understand a bit more now. I can use this information to hopefully learn more. Have a nice weekend. $\endgroup$ Commented Apr 9, 2022 at 23:14

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