# What is inductance?

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Like resistance is when there is hindrance towards the motion of electrons in an object. Then on similar lines what is inductance?

In: 19 Resistance to change in current flow.

Think like a train — it takes a lot of effort to get it going, but once it’s going it also takes a lot of effort for it to stop. The current moving through the inductor creates a magnetic field, as it moves through the wire coil, which slows the flow of current. The inductor’s value is related to the current that flows through it. (There are varying designs of inductors for different end-results — different sizes of wire coils, etc) The best way to imagine how an inductor works is a water propeller analogy.

The current speeds the propeller and while its speeding generates resistance, if the current stops the propeller will still move the current while its slowing down, if the current goes against the proppeller it will oppose more resistance but also try to chanage the way its spinning.

If the current changes the proppeller will oppose resistance to the change while also changing to match the current.

Inductors offer resistance in alternating current, in direct current they offer no resistance. Resistance slows all electrons that are trying to move through the device. Inductance only impacts electrons that are trying to change the current in the wire. In a DC circuit at steady state, the impact of an inductor is negligible. Reduce the current, the inductor tries to keep it going, much like a capacitor would. increase the current, or reverse the current, and the inductor resists the current change. Using the traditional analogy of the water hose, you can think of an inductor as a particular case where instead of water, the electrons are a non-Newtonian fluid, so the harder you push them the harder it is for them to move.

Inductance in this case is how hard the non-Newtonian fluid gets when you touch it. In other words, the higher the inductance the less the non-Newtonian fluid can change speed without becoming solid. Think of inductance as momentum.

The heavier an object, the more momentum it has, the slower it accelerates when pushed on by a force (it resists changes in velocity).

The more inductance a circuit has, the more it resists changes in current.

To bring another analogy (not related to pipes, or water flow). A circuit with a resistor, a capacitor and an inductor connected in series obeys *exactly* the same mathematics as a mass connected to a spring/dampener.

The inductance is mass. The capacitance is the spring stiffness and the resistance is the dampener coefficient.

The the amount of charge built up in the capacitor is equivalent to the displacement of the mass from the equilibrium position of the spring.

The current in the circuit is equivalent to the velocity of the mass. I like to think of Inductance as Inducing a current.

It uses the magnetic properties of electricity. So basically you have a regular electrical circuit somewhere near by and instead of using that power directly, you are using the magnetic field it is generating… that magnetic field can be made powerful enough to *induce* a new current flow in a completely unrelated circuit (even separated by great distance (feet)).

It isnt the most efficient form to run circuits but has many useful features and can be made more efficient for many applications. For example with induction cooktops… the energy isnt transferred via direct heat but instead heat is induced in the pots and pans. In that case… less energy is used because lots of heat is lost in direct resistive heat elements in cooking.

edit: also inductance and resistance really are not opposite things like you think. They are really not related in that way. An inductive circuit will also experience its own resistance not to mention the resistance lost in the inducing circuit. Its common to say that when you energize a circuit, the electrons travel super-fast, near the speed of light. However, in the first split second of energy flow, some of that energy it soaked up to form a small magnetic field.

A straight wire forms “some” magnetism, but if you wrap the wire in a coil, it focuses the magnetic field to make it stronger and more useful as a magnet.

When you turn the current off, that magnetic field collapses, and the magnetic energy is released in the form of a little bit of current. But since that current is added to the last little bit of system current, they can create a voltage spike that has a higher voltage than the system when it is at rest.

“Inductance” is the measurement of how much magnetic field the circuit produces, and it predicts how much of a voltage spike will happen when you turn it off. You might compare it to inertia.

You know you push something pretty heavy, it take a while to start to move, and then it become hard to stop.

It can be summarized by “the electric force that resists any change” Witch is a result of the electromagnetic force around the thing that has inductance.

When you use DC, you can generally ignore it. (Because once the circuit is running there is not change) you can’t ignore it when using AC.

One way to use it, is, for example, using it like a resistance, that will not let pass some frequencies but will let pass some (there are some formulas about that, but I won’t go into to much details)