# What do you call it when you add energy to an inductor?

When you add energy to a capacitor, you say that you are "charging it". (This is kind of a misnomer, since the total amount of charge in the capacitor is the same, but whatever.)

But what do you call it when you put current through an inductor, and it ________es up and forms a magnetic field?

Edit: Actually, using "charge" for a capacitor is not a misnomer, as shown below and in 'charge' etymology, though it leads to confusion, with people mistakenly thinking that capacitors store electric charge, when in actuality, the charge of energy just moves the electric charge from one plate to the other.

• What the flux? Had to say it. And I do not think saying you are charging it is a misnomer. You are causing a separation of charge and moving charge. I can see where the confusion comes from. – Kortuk May 19 '11 at 21:33
• @Kortuk: Well, "charging" a metal sphere in the context of electrostatics means adding net charge to it. "Charging" a capacitor or battery just means moving the charge from one place to another within the object. The net charge stays the same. – endolith May 20 '11 at 16:54
• and you get a capacitance when you charge a sphere between it and the ground. It is a poor capacitance so you are able to move a very large amount of charge and get a very high voltage. – Kortuk May 20 '11 at 17:23
• The term "charge" has been used to describe the addition of energetic stuff to many sorts of things (such as cannons) for a long time, even before the discovery of electricity. Indeed, I believe that the term "electrical charge" is derived from the more general usage. I see no reason to regard "charging an inductor" to be any more dubious usage than "charging a SCUBA tank". – supercat May 20 '11 at 19:41
• @supercat: You're right. charge (v.) early 13c., from O.Fr. chargier "to load, burden," from L.L. carricare "to load a wagon, cart," from L. carrus "wagon" (see car). Sense of "rush in to attack" is 1560s, perhaps through earlier meaning of "load a weapon" (1540s). Related: Charged; charging. Chargé d'affaires was borrowed from French, 1767, lit. "charged with affairs." – endolith May 20 '11 at 20:20

The word is simply energizing. It is actually used quite often when referring to superconducting magnets, which are nothing but inductors. http://en.wikipedia.org/wiki/Superconducting_magnet#Persistent_mode

• That works for capacitors, too, without the inaccuracy of "charging". – endolith May 20 '11 at 16:52
• Personally, I don't have too much reservations about charging, as literally "applying charge to some object" is far less often used than "moving some of the charges from one of the condenser's plates over to the other one", and it's just a matter of efficiency to use the shortest word for the most often used phrase. But it would certainly be more consequent to use energizing for both capacitors an inductors. – leftaroundabout May 20 '11 at 19:32
• @letaroundabout: True, but saying "charge a capacitor" misleads many people into thinking that capacitors store electric charge, which is wrong. "Energizing the capacitor" avoids this misconception. – endolith Sep 26 '11 at 19:27
• Nice correct term, but I find it shows a bit of affectation, at least in usual engineering context (in my experience). I find it more common to say to charge an inductor or to magnetize an inductor, although this latter is slightly incorrect, unless the inductor has a core that can actually be magnetized. – Lorenzo Donati -- Codidact.org Jan 16 '15 at 23:28

Putting energy into an inductor is called "energizing", and removing energy from it is "de-energizing".

I am going to take your question literally: " ...what do YOU call it when..." (emphasis supplied). Where I take your 'you' to be me.

I call it charging (and discharging). When I was in college my teachers and fellow students called it charging (and discharging). When I was at work designing electronics, we called it charging (and discharging). The guys who I rubbed elbows with, who wound their own toroids and built power supplies, called it charging (and discharging). I also (infrequently) heard the term "energize/energizing" used; and (rarely) de-energize. That may not be politically or technically correct; but that's how the guys (and gals) I worked with, who actually made the stuff that actually flew on airplanes and spacecraft (and, indeed, enabled them to fly), talked. Nothing wrong with energize/de-energize; but charging/discharging an inductor is perfectly acceptable vernacular.

Think about it from a systems or macro point of view: With a cap you push current into the device to store energy in an electric field. With an inductor you push current into the device to store energy in a magnetic field. With a battery you push current into the device to store energy in the form of a chemical reaction. Discharging extracts energy from whichever field or form is fundamental to the device. The inductor has the neat attribute that you can extract that energy without reversing current flow; but that fact does not demand an alternative word set to "charging/discharging,"

• There's nothing wrong with "charging an inductor". The word "charging" has a generic meaning of "to load up" or fill up. – endolith Jun 17 '11 at 18:28
• I would say I more often use the term charge but that energize is just as natural in conversation for me to hear. – Kortuk May 21 '12 at 13:52

The term "charge" was used to refer to loading things with other things long before anyone knew what an electron was; the term "electric charge" derives from the earlier usage, but hardly renders the earlier usage obsolete. The act of adding compressed gas to a fire extinguisher, for example, is referred to as "charging" it, even though no electrical potential difference is induced. I would thus consider it perfectly proper to use the term "charge" with an inductor.

• second favorite answer :) – endolith Jun 20 '11 at 20:12

I've heard the term "excitation" with respect to magnetics ... I personally use the term "ramping", as in current ramping up and ramping down.

There is energy stored in an inductor, namely $\frac{1}{2} * L * I^2$

For instance, it is used as energy storage in switching power supplies.

For lack of a better word, I would choose to call it charging. Also, wikipedia does not discern between capacitance and inductance in the article time_constant, which relates to the process of releasing charge.

• Afterthought: would it be okay to ask for the word on english.SE? – posipiet May 19 '11 at 21:02

At first I was going to suggest 'currenting' since it's somewhat the opposite of 'charging' (current vs. voltage). That doesn't sound right as a verb though. I want to go with 'spin' since it connotes a continuous movement (of current) through the device.

• Just be careful not to reverse the polarity of the neutron flow. – morten May 19 '11 at 20:54
• Current is a flow of charge, so it's not really an "opposite". Putting energy into a capacitor might more accurately be called "voltaging" :) – endolith May 19 '11 at 21:11
• "spinning up an inductor"? – endolith May 20 '11 at 16:51
• Yeah. It sounds cool anyway. – AngryEE Jul 3 '11 at 15:19
• That's all fine until you're dealing with a flux capacitor- Then what do you call it? – John D Jun 19 '14 at 21:40