magnetism, lawrents.

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Magnetism

Poles and attractive force of magnet

                Magnetic poles consist of two kinds, those are north pole (U) and south pole (S). the north pole of magnet always point to the north pole of the earth and the south pole of mahnet points to the north pole of earth.

We know that when identical poles of two magnet are brought close to each other, then two pole will repuls each other. Meanwhile, when the opposite poles are moved closer to each other, those pole will attratc each other.

Magnetic material and magnetic properties

Based on the strength of magnetic attractive force to a material or a body, then bodies in this nature are clasified into three kinds. Those are follows.

Feromagnetic bodies.namely bodies which are strongly attracted by magnets.

Paramagnetic bodies. Are weakly attracted by magnets. They are, aluminum, magnesium, platinum, manganese.

Diamagnetic bodies are not attracted or even tend to be repulsed by magnet. They are bismut, slk, coper, gold ect.

Meanwhile, based on the ability to store the magnetic property, magnets can be grouped into permanent and non permanent magnets.

Permanent magnet

Magnet  which are able to store their magnetic property for a long time are called permanent magnets. For example are hard metal which are difficult to change to magnet, but

Nonpermanent magnets.

Bodies that are not include into hard metals are easily made magnet but they also easily lose their magnetic property. (that kind of bodies is called “soft metals”, eventhough there is no metal that is realy soft. Magnet which are made of soft metal are called soft magnet (non-permanent magnets).

Magnetism theory and method to makr magnets

Magnetism theory

If a magnet is divided into small pieces, the pieces remain magnetic, and still have the north and aouth pole. So a magnet consists of tiny magnets which are called elementary magnets.

Earth magnetism teory

the earth is natural magnets. The north pole of earth magnets lies on the south pole of the earth and The south pole of earth magnets lies on the north pole of the earth.hence, a compas always point to the north and south direction.

The method to make a magnets

Scientist have found 3 methods to make a magnets, those are by rubbing, conduct electric current, and induction.

Rubbing methods.

A bar of iron or steel that is nonmagnetic can be made a magnets by beingg with a permanent magnet in one direction repeatedly.

Conducting electric current method

A piece of metals, such as iron can be made a magnets by winding a conductor wire covered by insulator material on the metal, then it is conduct by electric current.

Induction methods

A permanent magnets the magnetic property of which is strong can make a feromagnetic material that is not magnets become a magnets when it is brought close to, without touching, the feromagnetic materials.

The shape of magnets

The shape of magnets that are commonly found around us are. U-shape magnets, horse shoe, bar magnet, needle magnets.

Method to eleminate magnetic property

To eliminate the property of mahnet, that is by heating or hitting, when the magnet is heated or hit, the composition of the elementary magnet becomes irregular, so the magnetic property is lost.

Magnetic field

The pattern of line formed by magnet is the magnetic force line. The magnetic field line of two magnet when the idential poles are brought close to each other (N-N os S-S) and when the opposite poles are close the other (S-N or N-S), like figure.

Magnetic field around wire carrying electric current.

Hans Cristian Oersted made an experiment by showing the compas’s neddle always change position when it lay near conductor wire conducted with electric current. It can be conclude that around a wire carrying electric current a magnetic field is found; the direction of magnetic field depend on the direction of electric current passing through the conductor wire; the farther from the wire carrying current, the smaller the magnetic field strenght; and the bigger the lectric current, the stringer the magnetic field.

The direction of magnetic field lines around a wire carrying current can be deermine by two rule, those are:

Right-hand rule for electric current.

1. The thumbs shows the direction of electric current.
2. The other four finger show the direction of magnetic field lines aroun the wire that go around the conductor wire.

The clockwise screw rule.

1. The direction of screw turning determines the directiom of magnetic filed.
2. The linear direction of screw determine the direction current.

Magnetic fprce lines in a coil (solenoid) carrying electric current

To enlarge the magnetic field in a coil the following method can be done.

1. Increasing the current that flows in the coil.
2. Adding the winding of coil.
3. Inserting ferromagnetic body in the coil.

Electromagnet and its application.

Electric bell

Telephone

Magnetic relay

Transporter device of scrap irons.

Lorents force

The magnitude of Lorents force undergone by a wire crrying electric current depends on the following things.

1. The electric current (I) ampere
2. The length of wire (l) meter
3. Magnetic field strenght (B) tesla
4. The angle between electric currents ang magnetic filed ()

Lorents force can be formulate:

The relationship between Lorents force, magnetic field, and electric current can be expressed by the right-hand rule.

The working principle of Lorents force can be found in device such as electric motors, loud speaker, and galvanometer.