What makes an electromagnent work?

Question

Why does the flow of current looped many times around an iron bar create a magnetic field? Could it be accomplished without the iron bar in the center?

Answer 1

An electric current always emits a magnetic field, but coiling multiplies the effect. An iron bar also helps to magnify it, and it makes a good conductor for the magnetic energy. Here is a short introduction from wikipedia:

The simplest type of electromagnet is a coiled piece of wire. A coil forming the shape of a straight tube (similar to a corkscrew) is called a solenoid; a solenoid that is bent so that the ends meet is a toroid. Much stronger magnetic fields can be produced if a "core" of paramagnetic or ferromagnetic material (commonly iron) is placed inside the coil. The core concentrates the magnetic field that can then be much stronger than that of the coil itself.

Magnetic fields caused by coils of wire follow a form of the right-hand rule. If the fingers of the right hand are curled in the direction of current flow through the coil, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the north pole.

Answer 2

The electromagnetic effect occurs any time you have current running through a conductor. The magnetic field will always form around the conductor and the polarity is dependent on the direction of current flow. By looping the wire into a coil, you intensify the magnetic field by causing it to join up with the field generated by the next loop of coil. It works without the iron bar in the center, but the metallic core helps to focus the magnetic field at the end, by channelling the force lines passing through the center of the coil. Besides, when you're picking things up, it's easier to handle if they stick to the solid iron bar rather than to the electric coils.

Answer 3

Consider a small bar magnet; it has two poles north and south.

Place another similar magnet on it with north poles coinciding.

The power of the magnet increases. Adding a number of magnets like this will increase the total power.

Therefore, we can imagine a single bar magnet as if it is made of many number of thin bar magnets.

Now consider a small loop of circular wire which has current in it.

This, in no way, differs from a magnet. The axis of the coil acts like a magnet; on one side of the magnet there is North Pole and on the other side, there is South Pole.

Thus a single loop is a magnet. If we have many number of loops, it is as if we are adding magnets as explained above; the total strength of this ‘electro-magnet’ increases.

In the previous example, when we added a number of bar magnets side by side and one above the other, the total size of the magnets are increased. But we can replace all these magnets by single small sized bar magnet which will give the same power as the combined magnets. That is in the new magnets all the magnetic fields are compressed to small cross- sectional area.

The same happens when we place an iron piece in the electro- magnet. The fields due to different loops are confined to a small cross sectional area ( cross-section of the iron piece).

Answer 4

A magnetic field is created whenever an electric charge moves. The problem is that most electric charges in nature are moving in random directions, so they tend to cancel out. For example, every electron in an atom creates a magnetic field, but they usually move in random directions so the fields cancel.

Electromagnetism is produced by causing a current (moving electrons through a wire). If wire is wrapped so that the electrons move in the same direction (such as all move clockwise) so their magnetic effect will not cancel out, they will also exert a force on other moving electrons in atoms such as iron where the motion of the electrons does not cancel out.

The wire has to be looped in the same direction so that the magnetic fields of each loop will add together instead of canceling each other out.

The iron bar in the center is used to amplify the magnetic field. Iron is one of those few substances where the electrons orbiting the nucleus do not completely cancel out the magnetic field - iron molecules are said to have a "magnetic moment." This means that if you place the iron atoms in a magnetic field, they will tend to orient themselves in such a way that the iron atoms will constructively add to the magnetic field.

Yes, you can create a magnetic field without the iron bar - but the field will probably be much weaker.

Answer 5

The magnetic fields caused by running a current thru the windings in the magnet are flowing thru the business end of your magnet.

Answer 6

current always creates a magnetic field. The windings magnify that effect. yes it can(don't need iron bar)