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Can you explain to me how electric currents can produce magnetic effects, and how magnets can cause electric currents?
Question Date: 2013-05-10
Answer 1:

Since science is primarily based on the observation and description of the natural world, science does not yet really tell us why certain things happen at the most basic level.

Electromagnetism is one of these basic ideas that is known to be true (and has been studied for more than 200 years!), and modern scientists have a very good idea about how electric and magnetic effects are related. The question of why these effects are so tightly linked has remained extremely hard to prove.

We can, however, use the relationships between electricity and magnetism that have been developed to explain many interesting things that happen in the world around us! For example, scientists can tell exactly how far a compass needle will deflect when placed near a wire that is carrying electricity. We can also use these ideas to make many important technologies, such as hard disc drives for computers.

I know that electromagnetism can be tricky to think about - I certainly think so! - but I hope that I have been able to help answer your question. Please send along any other questions that come to mind!

Answer 2:

This is an excellent question and one which has two answers, neither of which is a very good answer. But knowing the two answers and how they relate gets to the very heart of what science is and can help us realize just how wonderful and amazing the universe can be. Sounds like a tall order right... well, let me try to explain.

So I said that there are two answers to your question. Both are completely right and 100% true, so far as we can tell, and they've been tested quite a bit. Understanding both these answers, and how they can both be true is what discovering the universe is all about. But let's get to these answers already. I'll start with the longer answer, so that you can keep it in mind while reading the shorter answer. The question is "can you explain to me how electric currents can produce magnetic effects, and how magnets can cause electric currents?" and if you're asking what is it about electric currents that cause magnetic effects, and what is it about magnets that cause electric currents, then the answer is that I can provide no insight on those questions.

I cannot explain why these things are the case, and it's not for lack of study. The truth is that nobody can answer those questions. The fact of the matter is that scientists have studied these things at great length, and we know that it is indeed the case, that when a magnet moves in proximity to a loop of wire, it exerts a force on the electrons within that loop which causes a current. We know that it happens and we can explain what exactly is happening and have very carefully calculated values for how much current will flow for a given magnet in a given situation. We know all those things very precisely. (That is basically the second answer, which I will go into a little bit later.) But the fact still remains that we are only describing what we see (or observe) in nature.

The fact of the matter is that electric and magnetic fields are one in the same, an electrical charge (like an electron) in motion causes a magnetic field, and a magnetic field in motion causes an electric field. But why this is the case can only be answered by the words... "The universe is that way". The force responsible for both electrical effects and magnetic effects is called the electro-magnetic force (I wonder where they got the name, right?!?). Scientists call it one of 4 fundamental forces (actually in reality there are 3 fundamental forces, but in the world as we see it 1 of those forces splits off to behave in two different ways... but that's a detail you can ignore until you start doing a Ph.D. in physics).

We call these forces fundamental because they exist and are not caused by anything else. Gravity is another fundamental force. It's true that gravity comes from large massive objects, like the earth, but if you ask why mass produces gravity, the answer is just because that's the way the world works. Matter pulls other matter towards it through gravity. Just like a moving electron produces a magnetic field. It's just a funny little thing that the universe does. And to try to understand why this is the case is sort of like asking what color is my voice. It's the wrong sort of question to be asking.

Scientists have spent a lot of their time figuring out how electro-magnetism works, but none would even try to answer why it works. As far as we know, the universe could have made had it some other way. The fact that everything works out so nicely and life seems to work out well for us seems almost unlikely, given the the universe could have been any other way. To some, this is proof that something must have created, at least the rules of the universe. To others, the universe is this way because if it were any other way, then we wouldn't be around to ask the question of why the universe seems to work out so nicely. This is called the anthropic principle.

Many scientists believe that our universe is just one of many, that either exist at the same time as ours, or have existed at some point in the past. In any universe where the conditions aren't right for life, there just won't be any life to observe that universe, and so we'll never know about it. For examples, if there is a universe where electrons don't repel each other, which by the way, is what keeps you from passing through solid objects, then we would never know because life wouldn't be able to develop there and so we wouldn't know about it.

So, that's the long answer: I cannot explain it because it simply is how the universe works. That's the puzzle scientists grapple with everyday. Read the next answer on Answer 3 below.

Answer 3:

The other answer relates to how electric effects produce magnetic ones and viceversa. As I mentioned, electric and magnetic phenomena are tightly coupled. You can think of them as two sides of the same coin. It's not really that one causes the other, they just happen to always go together. Scientists have observed that a changing electric field creates a magnetic field. So, if you have a circuit and you send AC current through (AC = Alternating current) so that the electrons move back and forth, they will create a changing electric field. This produces a magnetic field (because that's what the universe does). Similarly a changing magnetic field creates an electric field. Luckily enough we have a changing magnetic field, we just created it with our AC current. It went from 0 to some non-zero amount, and so that change is enough to create an electric field. And, as you can guess, the creation of that electric field creates a magnetic field, etc. etc. There is a good illustration of it on this web site.

EM propagation

We can also write equations to give us precise measurements for how strong the fields are, but all the equations we have for electromagnetics are empirical. That means that we went out into the world and measured things, and then found a formula that seems to agree with all of the data we collected. But as far as we can tell, our equations do pretty well. It's also important to note that while electromagnetic waves can travel through materials by jiggling around the electrons as the wave passes through, the material is not necessarily. Electromagnetic waves can travel through complete vacuum (ie: nothingness, no air, no material, no anything). It's a good thing that's the case, because the electromagnetic waves coming from the sun (light and heat) need to travel through the nothingness of space to reach us.

So, that is my answer to your question: I can describe what's happening, but I cannot explain it. Changing Electric fields produce magnetic fields and viceversa. That's the way the universe works.

Thanks for the question.

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