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UNIT I
MAGNETISM
Text I
Useful terms. Read and memorize the following words and word combinations.
attract
bismuth
carbon graphite
charged particles
cobalt
Curie temperature
diamagnetic materials
electric circuit
ferromagnetic materials
flow ,
gadolinium
iron
living tissue ()
Lorentz force
magnetic field
magnetic flux
magnetic force
nickel
repel, repulse
spin ,
2 
Work in pairs. Discuss with a partner the following items. While speaking use the given expressions.
- Magnetic field origin
- Magnetic flux determination
- Interaction of magnets
- Magnetic materials
| I believe | To begin with |
| In my opinion | Firstly |
| I think | Secondly |
| In my view | Thirdly |
| From my point of view | Finally |
| It seems to me that |
|
|
|
3 
Read the text and check your ideas.
Magnetism
Magnetism is a force that acts at a distance and is caused by a magnetic field. This force strongly attracts ferromagnetic materials such as iron, nickel and cobalt. In magnets, the magnetic force strongly attracts an opposite pole of another magnet and repels a like pole.
A magnetic field consists of imaginary lines of flux coming from moving or spinning electrically charged particles. Examples include the spin of a proton and the motion of electrons through a wire in an electric circuit.
The lines of magnetic flux flow from one end of the object to the other. By convention, we call one end of a magnetic object the N or North-seeking pole and the other the S or South-seeking pole, as related to the Earth's North and South magnetic poles. The magnetic flux is defined as moving from N to S. The magnetic flux, symbol , produced by a magnet or electromagnet is a measure of the magnetic field and has the unit of the weber (Wb). Magnetic flux is the product of the average magnetic field (B) times the perpendicular area (A) that it penetrates. That is: =BA
The magnetic field of an object can create a magnetic force on other objects with magnetic fields. That force is what we call magnetism.
When a magnetic field is applied to a moving electric charge, such as a moving proton or the electrical current in a wire, the force on the charge is called a Lorentz force.
When two magnets or magnetic objects are close to each other, there is a force that attracts the poles together.
Magnets also strongly attract ferromagnetic materials such as iron, nickel and cobalt.
When two magnetic objects have like poles facing each other, the magnetic force pushes them apart.
Magnets can also weakly repel diamagnetic materials.
