# Help Understanding Inductors in DC Circuits

So this is what I know about inductors. I know that they "store" energy in their magnetic fields, they are resistant to change in current (dI/dt), they act like regular wires if the current becomes constant (so no magnetic field right?), and that the reason they oppose a change in the direction of the current is because a difference in voltage (an emf) caused by the change in the magnetic field which is due to a change in current as time passes? (Most important question) So I guess my question is, how exactly is there a change in current, would that only happen when we supply and cut off current from the circuit? Also if I use the one of the hand rules on a inductor and find the direction of the force, would that be the direction in which the inductor is opposing the current?

Diagrams that include the direction of the force in a circuit with an inductor and its magnetic fields would help.

• It's not clear to me what your question is. Your title states this is about DC circuits and your question goes on about asking about changing currents. Then you ask about force aswell. So really, what is your specific question? I think the problem is that you are trying to think about everything at once. – null Aug 31 '16 at 23:19
• @null By changing currents I meant dI/dt and how it relates to inductors in a DC circuit. By force I meant if that was what made an inductor resist the change in current, again dI/dt, or if it was the voltage created by the inductor or if it was the same thing (force = voltage) in this context since an EMF = voltage and EMF stand for electromotive force. If you can't answer the previous questions just answer me this, how exactly is there a change in current, would that only happen when we supply and cut off current from the circuit? – El Psy Congroo Sep 1 '16 at 0:43

I know that they "store" energy in their magnetic fields,

No need for scare quotes - the energy stored by in inductor is in its associated magnetic field.

they are resistant to change in current (dI/dt),

I like oppose rather than resist due to the possible confusion with resistance which is dissipative.

they act like regular wires if the current becomes constant (so no magnetic field right?)

no changing magnetic field when the current is constant but there is a non-zero magnetic field associated with the non-zero current through.

and that the reason they oppose a change in the direction of the current is because a difference in voltage (an emf) caused by the change in the magnetic field which is due to a change in current as time passes?

The changing magnetic field threading the inductor, due to the changing current, produces an emf which separates charge thus producing a voltage across the inductor.

(Most important question) So I guess my question is, how exactly is there a change in current, would that only happen when we supply and cut off current from the circuit?

Consider placing an ideal, charged capacitor across an ideal inductor. The current through the inductor will be sinusoidal (assuming no significant radiative losses). Image credit