5 Difference Between Bar Magnet And Electromagnet

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Electromagnets

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A wire with an electric current (charged electrons) produces a magnetic field in its surroundings. The strength of the magnetic field depends on the intensity of the current and the shape of the wire. Each wire with a current flow is practically an electromagnet.

The orange arrow indicates the technical direction of the current. Historically, it is opposite of the direction of the electrons.

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Coils

If you bend the wire with the current flow into a circle, it creates a magnetic field with poles (see picture). Therefore, a circulating current creates a magnet with a north and south pole.

In common magnets the wire is often wound into a multi-layered coil, which is also called solenoid.

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A wire coil with north and south pole

Electromagnets

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A wire with an electric current (charged electrons) produces a magnetic field in its surroundings. The strength of the magnetic field depends on the intensity of the current and the shape of the wire. Each wire with a current flow is practically an electromagnet.

The orange arrow indicates the technical direction of the current. Historically, it is opposite of the direction of the electrons.

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Coils

If you bend the wire with the current flow into a circle, it creates a magnetic field with poles (see picture). Therefore, a circulating current creates a magnet with a north and south pole.

In common magnets the wire is often wound into a multi-layered coil, which is also called solenoid.

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A wire coil with north and south pole

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Soft-iron core (grey) with coil (orange)

Soft-iron core

When it comes to electromagnets, usually a soft-iron core is placed in the coil, which considerably strengthens its magnetic field, because the magnetic field of the coil magnetises the soft-iron core and, thereby, creates an additional magnet. The soft-iron core loses its magnetisation after the current is turned off. This is desirable in order to be able to turn the magnet on and off.

Magnetically soft and hard iron

The term magnetically "soft" is based on the fact that mechanically soft iron loses its magnetisation, while the mechanically hard iron (steel) that is carbon-enriched keeps part of its magnetisation. This is called remanence. The latin word "remanere" means "to remain". Material with high remanence is referred to as "magnetically hard".

Solenoids with a current flow magnetise also permanent magnets, like our super magnets, which are all made of magnetically hard material.

Permanent magnets

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Electron with a spin: A microscopic magnet

Electron spins

In permanent magnets the B fields are also created through currents. But these currents are not macroscopic currents, in which charged particles flow in one direction. They are microscopic electric currents, which, in the case of ferromagnetism, are created through certain electrons rotating around themselves in the material (electron spins). An electron spin can be viewed as a microscopic small circulating current.

Strengths of permanent and electromagnets

The strength of a magnetic field of an electromagnet depends on the core material, the number of solenoid windings and the intensity of the current. With a high enough amperage the electromagnet can develop a significantly stronger magnetic field than a permanent magnet.image

Left: A permanent magnet with field lines

Right: An electromagnet with power source (left), solenoid (orange) and soft-iron core (middle)

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Soft-iron core (grey) with coil (orange)

Soft-iron core

When it comes to electromagnets, usually a soft-iron core is placed in the coil, which considerably strengthens its magnetic field, because the magnetic field of the coil magnetises the soft-iron core and, thereby, creates an additional magnet. The soft-iron core loses its magnetisation after the current is turned off. This is desirable in order to be able to turn the magnet on and off.

Magnetically soft and hard iron

The term magnetically "soft" is based on the fact that mechanically soft iron loses its magnetisation, while the mechanically hard iron (steel) that is carbon-enriched keeps part of its magnetisation. This is called remanence. The latin word "remanere" means "to remain". Material with high remanence is referred to as "magnetically hard".

Solenoids with a current flow magnetise also permanent magnets, like our super magnets, which are all made of magnetically hard material.

Permanent magnets

image

Electron with a spin: A microscopic magnet

Electron spins

In permanent magnets the B fields are also created through currents. But these currents are not macroscopic currents, in which charged particles flow in one direction. They are microscopic electric currents, which, in the case of ferromagnetism, are created through certain electrons rotating around themselves in the material (electron spins). An electron spin can be viewed as a microscopic small circulating current.

Strengths of permanent and electromagnets

The strength of a magnetic field of an electromagnet depends on the core material, the number of solenoid windings and the intensity of the current. With a high enough amperage the electromagnet can develop a significantly stronger magnetic field than a permanent magnet.

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Left: A permanent magnet with field lines

Right: An electromagnet with power source (left), solenoid (orange) and soft-iron core (middle)

The bar magnet is what is termed a permanent magnet . This means that it is "always on" and can be used to do things like pick up paper clips. The electromagnet is created by winding a coil of wire about a ferromagnetic core and running a direct current through that coil. Only when the current is flowing will the electromagnet be operating. With the current switched off, the magnetic field around the coil of wire disappears, and the power of the electromagnetic disappears as well.

Electromagnet 

  1. Behaves like a magnet till the current flows through it.
  2. Can be demagnetized 
  3. Polarity  can be changed 
  4. Magnetic strength can be changed 

Permanent  magnet 

  1. It is a permanent magnet 
  2. Cannot be demagnetized 
  3. Polarity is fixed
  4. Magnetic strength is fixed