# Electric current and magnetic field relationship

### Magnetic field created by a current carrying wire (video) | Khan Academy

Electric current flowing through a single loop of wire does not generate a very powerful magnetic field. A coil of wire looped many times makes. A magnetic field is a vector field that describes the magnetic influence of electrical currents and . steady current. Also in this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism. The magnetic field lines around a long wire which carries an electric current form concentric circles around the wire. The direction of the magnetic field is.

Flipping a bar magnet is equivalent to rotating its m by degrees. The magnetic field of larger magnets can be obtained by modeling them as a collection of a large number of small magnets called dipoles each having their own m.

The magnetic field produced by the magnet then is the net magnetic field of these dipoles. And, any net force on the magnet is a result of adding up the forces on the individual dipoles. There are two competing models for the nature of these dipoles.

## Electric current and magnetic field

These two models produce two different magnetic fields, H and B. Outside a material, though, the two are identical to a multiplicative constant so that in many cases the distinction can be ignored. This is particularly true for magnetic fields, such as those due to electric currents, that are not generated by magnetic materials. Magnetic pole model and the H-field[ edit ] The magnetic pole model: It is sometimes useful to model the force and torques between two magnets as due to magnetic poles repelling or attracting each other in the same manner as the Coulomb force between electric charges.

This is called the Gilbert model of magnetism, after William Gilbert. In this model, a magnetic H-field is produced by magnetic charges that are 'smeared' around each pole.

These magnetic charges are in fact related to the magnetization field M. The H-field, therefore, is analogous to the electric field E, which starts at a positive electric charge and ends at a negative electric charge. Near the north pole, therefore, all H-field lines point away from the north pole whether inside the magnet or out while near the south pole all H-field lines point toward the south pole whether inside the magnet or out.

Too, a north pole feels a force in the direction of the H-field while the force on the south pole is opposite to the H-field. The magnetic pole model predicts correctly the field H both inside and outside magnetic materials, in particular the fact that H is opposite to the magnetization field M inside a permanent magnet.

Since it is based on the fictitious idea of a magnetic charge density, the Gilbert model has limitations. If a magnetized object is divided in half, a new pole appears on the surface of each piece, so each has a pair of complementary poles. The magnetic pole model does not account for magnetism that is produced by electric currents. Amperian loop model and the B-field[ edit ] See also: Gauss's law for magnetism The Amperian loop model: A current loop ring that goes into the page at the x and comes out at the dot produces a B-field lines.

The north pole is to the right and the south to the left. If the majority number of electrons in the atom spins in the same direction, a strong magnetic field is produced. The direction of the electrons spin determines the direction of magnetic field. On the other hand, if the equal number of electrons in the atom spins in the opposite direction, the spinning speed of the electrons cancels out.

Thus, the magnetism also cancels out. Relationship between electricity and magnetism In the early days scientists believed that, electricity and magnetism are two separate forces. However, after the publication of James Clerk Maxwell, these forces are treated as interrelated forces.

InHans Christian Orsted observed a surprising thing, when he switched on the battery from which the electric current is flowing, the compass needle moved away from the point north.

Magnetic field created by a current carrying wire - Physics - Khan Academy

After this experiment, he concluded that, the electric current flowing through the wire produces a magnetic field. Electricity and magnetism are closely related to each other.

• Magnetic field created by a current carrying wire

The electric current flowing through the wire produces a circular magnetic field outside the wire. Electric motors Video transcript So not only can a magnetic field exert some force on a moving charge, we're now going to learn that a moving charge or a current can actually create a magnetic field. So there is some type of symmetry here. And as we'll learn later when we learn our calculus and we do this in a slightly more rigorous way, we'll see that magnetic fields and electric fields are actually two sides of the same coin, of electromagnetic fields.

But anyway, we won't worry about that now. And I think it's enough to ponder right now that a current can actually induce a magnetic field. And actually, just a moving electron creates a magnetic field. And it does it in a surface of a sphere-- I won't go into all that right now. Because the math gets a little bit fancy there. But what you might encounter in your standard high school physics class-- that's not getting deeply into vector calculus-- is that if you just have a wire-- let me draw a wire.

And it's carrying some current I, it turns out that this wire will generate a magnetic field. And the shape of that magnetic field is going to be co-centric circles around this wire.

## Magnetic field

Let me see if I can draw that. So here I'll draw it just like how I do when I try to do rotations of solids in the calculus video. So the magnetic field would go behind and in front and it goes like that. Or another way you can think about it is if-- let's go down here-- is on the left side of this wire. If you say that the wire's in the plane of this video, the magnetic field is popping out of your screen.

And on this side, on the right side, the magnetic field is popping into the screen. It's going into the screen. And you could imagine that, right? You could imagine if, on this drawing up here, you could say this is where it intersects the screen. All of this is kind of behind the screen. And all of this is in front of the screen. And this is where it's popping out.

And this is where it's popping into the screen. Hopefully that makes a little bit of sense. And how did I know that it's rotating this way? Well, it actually does come out of the cross product when you do it with a regular charge and all of that. But we're not going to go into that right now. And so there's a different right hand rule that you can use. And it's literally you hold this wire, or you imagine holding this wire, with your right hand with your thumb going in the direction of the current.

And if you hold this wire with your thumb going in the direction of the current, your fingers are going to go in the direction of the magnetic field.

### Relationship Between Electricity & Magnetism | Sciencing

So let me see if I can draw that. I will draw it in blue. So if this is my thumb, my thumb is going along the top of the wire. And then my hand is curling around the wire. Those are my knuckles. Those are the veins on my hand. This is my nail. So as you can see, if I was holding that same wire-- let me draw the wire. So if I was holding that same wire, we see that my thumb is going in the direction of the current.