# Question in relation to Transformers and Inductors

#### Rolland B. Heiss

Joined Feb 4, 2015
236
Today after work I looked up several things after taking apart a few items in order to salvage components (as always please pardon my ignorance) and noticed that transformers and inductors seem similar in a way, despite the fact that they seem to do differing things. What makes the difference in relation to Faraday's law they both seem to follow? The secondary winding on the transformer as opposed to the singular winding on the inductor? Or is there more to it than my basic observation? What if I put a secondary winding on an inductor? Would it become sort of a transformer? Please be patient in the midst of my curiosity and ignorance but I really want to learn!

#### sjgallagher2

Joined Feb 6, 2013
131
You've got the right style on this board haha most have been kicking around in electronics too long and lose their sense, they come out a bit rude but they always mean well. To answer your question, though I don't know how much you know, transformers have two windings around the same core, and inductors have one winding around a core. They both have coils, they use them differently though. Inductors, single coils, are used to block high frequency signals. That works because of iductive reactance which means that the inductor, when you put AC through it, acts like a resistor. Caps do the same thing. As you go higher in frequencies, say from 60Hz line voltage to 100MHz you might see in a radio, the resistance goes up. Eventually it's so large (100M) that it looks like an open, meaning current can hardly get through. Bonus points, capacitors do the opposite- they have infinite resistance (reactance) at DC (0 Hz) and look like a short circuit at higher frequencies. That means you can short different components at AC but not for DC. That comes in handy when you design amplifiers with transistors, because of whats called "biasing" but that's a topic for another day... Transformers don't use inductive reactance in their operation. It's just negligible. Instead they use another property of coils, where one coil can "induce" a voltage in another. So if I put in 120VAC to one coil, the other might come out as 120VAC even if they're not connected at all. It radiates. The best part is that you can change how much voltage actually gets passed by messing with the number of times you wrap the wires. It's linear too, like if you wrap one coil 10 times and the other 3 times, then only 3/10ths of that voltage goes through. So I can use a transformer to take the 120VAC from an outlet to create 12.5VAC that I can handle without getting too much heat from resistors and diodes and things. This whole induction idea for transformers is faraday's law. Inductors don't use it. It's negligble in inductors. Hope I've helped you understand anything, I'm always learning to teach better on here haha. Oh by the way, if you wrap another coil around an inductor it will become a transformer, though who knows how good it'll be. The different ways they throw transformers together come from efficiency only, meaning a toroid transformer and a transformer you see in a power line and one in a power supply all do the same thing, but the way the math works out they do some things better than others. It has to do with magnetic coupling or some such thing, magnetic "lines" meaning the amount of strength magnets have at different places, and how they interact with "cores" which are pieces of ferrite metals, metals that magnets stick to, that are in or around the coils. ~Sam Gallagher

#### sjgallagher2

Joined Feb 6, 2013
131
Well okay, inductors use faradays law when you look at the physics, but for practical purposes you can ignore it. For the physics part, the capacitor creates a magnetic field, which cuts into surrounding wires going to the inductor, and create "back-EMF" which resists a change in current. I don't understand that bit well anymore, because it's virtually useless knowledge in practical electronics, where I've been for a while now...

#### Rolland B. Heiss

Joined Feb 4, 2015
236
You've got the right style on this board haha most have been kicking around in electronics too long and lose their sense, they come out a bit rude but they always mean well. To answer your question, though I don't know how much you know, transformers have two windings around the same core, and inductors have one winding around a core. They both have coils, they use them differently though. Inductors, single coils, are used to block high frequency signals. That works because of iductive reactance which means that the inductor, when you put AC through it, acts like a resistor. Caps do the same thing. As you go higher in frequencies, say from 60Hz line voltage to 100MHz you might see in a radio, the resistance goes up. Eventually it's so large (100M) that it looks like an open, meaning current can hardly get through. Bonus points, capacitors do the opposite- they have infinite resistance (reactance) at DC (0 Hz) and look like a short circuit at higher frequencies. That means you can short different components at AC but not for DC. That comes in handy when you design amplifiers with transistors, because of whats called "biasing" but that's a topic for another day... Transformers don't use inductive reactance in their operation. It's just negligible. Instead they use another property of coils, where one coil can "induce" a voltage in another. So if I put in 120VAC to one coil, the other might come out as 120VAC even if they're not connected at all. It radiates. The best part is that you can change how much voltage actually gets passed by messing with the number of times you wrap the wires. It's linear too, like if you wrap one coil 10 times and the other 3 times, then only 3/10ths of that voltage goes through. So I can use a transformer to take the 120VAC from an outlet to create 12.5VAC that I can handle without getting too much heat from resistors and diodes and things. This whole induction idea for transformers is faraday's law. Inductors don't use it. It's negligble in inductors. Hope I've helped you understand anything, I'm always learning to teach better on here haha. Oh by the way, if you wrap another coil around an inductor it will become a transformer, though who knows how good it'll be. The different ways they throw transformers together come from efficiency only, meaning a toroid transformer and a transformer you see in a power line and one in a power supply all do the same thing, but the way the math works out they do some things better than others. It has to do with magnetic coupling or some such thing, magnetic "lines" meaning the amount of strength magnets have at different places, and how they interact with "cores" which are pieces of ferrite metals, metals that magnets stick to, that are in or around the coils. ~Sam Gallagher
Great response Sam! I learned a great deal by reading your kind and informative answer. Thanks!!!

#### Rolland B. Heiss

Joined Feb 4, 2015
236
Well okay, inductors use faradays law when you look at the physics, but for practical purposes you can ignore it. For the physics part, the capacitor creates a magnetic field, which cuts into surrounding wires going to the inductor, and create "back-EMF" which resists a change in current. I don't understand that bit well anymore, because it's virtually useless knowledge in practical electronics, where I've been for a while now...
No worries, I'm still meddling in impractical electronics!

#### Rolland B. Heiss

Joined Feb 4, 2015
236
Now that I think of it and since capacitors were mentioned I've got another question. Not long ago I hacked an old hand crank flashlight in order to turn it into a hand crank generator in order to charge capacitors and such. Today for example I pulled a 6800uF 25V capacitor from something and charged it to a little over 9V and hooked it up to my radio. The radio worked for about 5 seconds and the power was lost. Is there a way to use the 9V in the capacitor for an extended period of time or do capacitors always release everything so quickly, thus making them very poor potential battery replacements? The cool thing though was that for those 5 seconds or so the signal was excellent!

#### MrChips

Joined Oct 2, 2009
21,634
A capacitor is like a tank of water but instead of holding water a capacitor holds charge.

How long the tank of water holds water depends on the size of the tank and the size of the tap from which you draw water. The larger the water tap, the shorter the time.

Similarly, the length of time it takes to drain the charge from the capacitor depends on its size and how much charge you are draining. The more current you take the shorter the time.

#### Rolland B. Heiss

Joined Feb 4, 2015
236
A capacitor is like a tank of water but instead of holding water a capacitor holds charge.

How long the tank of water holds water depends on the size of the tank and the size of the tap from which you draw water. The larger the water tap, the shorter the time.

Similarly, the length of time it takes to drain the charge from the capacitor depends on its size and how much charge you are draining. The more current you take the shorter the time.
I can visualize that MrChips. I'm a very visual person and therefore this makes perfect sense to me. I'm not so good at reading lines on a page that explain things others would easily understand if those lines create no visuals in my mind. If I can see someone do something I can replicate it easily. If someone tells me how something can be done and I'm unable to visualize it I have a very difficult time replicating it! Take my old Coleman Evcon heating unit for example. I know nearly everything there is to know about it after paying a certain repair guy hundreds of dollars to come and fix it over the years but I watched everything he did! So the next time this or that went out I fixed it myself for a song coupled with a few burnt calories. Interestingly enough, all those times I paid that guy to fix my central heating I kept telling him that little to no air was coming out of the vents and I wondered why and he always had some answer that didn't make sense to me as he confidently told me that everything is working fine. Sure, the electronics were working fine but he should have spoken of the possibility of a plugged up A coil. He never did. So last winter I barely got by after paying for two cords of wood (which is all I could afford) since I happen to have a fireplace and the winter wasn't very pleasant at times because you cannot stay up 24 hours a day keeping the fire going! There are also two tropical birds living here as well and we're lucky they are still alive. Anyway, last summer I figured out where the A coil was and how to access it. Wasn't easy but the tin snips I bought for that project have come in handy in the course of my recent electronic experiments here and there! There was so much crap caked on those coils once I got to them that it is amazing any air (however miniscule) even managed to make it out of the vents. Here I was fretting about how the hell I was going to afford a new central heating unit last winter I wouldn't be able to afford when all the while the main problem was merely a terribly dirty A coil! So I figured it all out on my own and now the heater works better than when I bought the place about 10 years ago. Reminds me of the old saying which in my estimation is a great saying: "If you want something done right then do it yourself!". However, it does help when you know what you are doing to begin with! This leads me to another saying I like very much... "Necessity is the mother of invention.".

Anyway, pardon me for responding with what could be considered akin to Tolstoy's War and Peace! If you read all of this I hope it didn't age you further. As for me, during the course of typing this I have several new gray hairs!

In other words, thanks and sorry at the same time.

#### WBahn

Joined Mar 31, 2012
26,047
Today after work I looked up several things after taking apart a few items in order to salvage components (as always please pardon my ignorance) and noticed that transformers and inductors seem similar in a way, despite the fact that they seem to do differing things. What makes the difference in relation to Faraday's law they both seem to follow? The secondary winding on the transformer as opposed to the singular winding on the inductor? Or is there more to it than my basic observation? What if I put a secondary winding on an inductor? Would it become sort of a transformer? Please be patient in the midst of my curiosity and ignorance but I really want to learn!
A transformer is nothing more than two inductors positioned so that the magnetic field created by one is seen by the other. The coupling is called "mutual inductance". A single coil has "self-inductance" which means that it induces a voltage in itself as a result of the changing magnetic field it creates as the current in it changes. Mutual inductance is simply when a coil has the same effect in another coil. Any two conductors have both self-inductance and mutual-inductance. Most of the time, both are small enough as to be neglected. In the case of your normal inductors, the self-inductance is big enough to matter, but the mutual-inductance to all of the other conductors is still small enough to be neglected. But if you position them carefully, you can make the mutual-inductance large and, voilà, you have a transformer. At other times, you may not want the mutual-inductance to be big enough to matter, but you are working with a circuit that is sensitive enough that it does matter. Then you take steps to minimize the unwanted mutual-inductances.