Magnetic Force Lines in a Coil (Solenoid) Carrying Electric Current

To get a stronger magnetic field, a rolled (wound) conductor wire is used so it forms a longitudinal circle called coil (Solenoid). If the cavity of a coil (solenoid) is filled with bodies which are ferromagnetic, the magnetic field will be bigger than when it is not filled with ferromagnetic bodies. To enlarge the magnetic field in a coil the following method cam be done 

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

Reference:
Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

Magnetic Field Around a Wire Carrying Electric Current

To prove that arround a wire carrying electric current there is a magnetic field, then a physicist named Hans Cristian Oersted (1777-1851), made an expriment in 1820 by showing that the compss’s needle always changed position when it lay near a condctr wire conducted with electric current.

Based on Oersted’s experiment, it can be concluded that around a wire carrying electric current a magnetic field is found; the direction of magnetic field depends on the direction of electric current passing through the conductor wire; the farther from the wire carrying current, the smaller the magnetic field strength; and the bigger the electric current, the stronger the magnetic field.

The direction of magnetic field lines around a wire carrying current can be determined by two rules, those are;

1.    Right-hand rule for electric current
       (a)    The thmb shows the direction of electric current
       (b)    The other four fingers show the direction of magnetic field lines around the wire that go
               around the conductor wire

2.    The clockwise screw rule
        (a)    The direction of screw turning detrmine (indictes) the direction og magnetic field
        (b)    The linear direction of screw determines the direction of current.

Reference:
Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

The Methods to Make a Magnet

1. Rubbing Method: A bar of iron or steel that is nonmagnetic can be made a magnet by being rubbed with a permanent magnet in one direction repeatedly. 
2. Conducting Electric Current Method: A piece of metal, such as iron can be made a magnet by winding a conductor wire covered by insulator material on the metal, then it is conducted by electric current. 
3. Induction Method: A permanent magnet the magnetic property of which is strong can make a ferromagnetic materal that is not magnet become a magnet when it is brought close to, without touching, the ferromagnetic materials. 
4. The Shapes of Magnet: Until this time, magnets are made in several forms. Meanwhile the shapes of magnet that are commonly found around us, among others, are U-shaped magnet, bar magnet, horse shoe-shaped magnet, and needle magnet. 
5. Method to eliminate magnetic property: Not only can you make a magnet, but also eliminate the magnetic property of magnet, that is by heating (burning) or hitting (dropping). Why can the two processes eliminate the magnetic property of a material?. In the permanent magnet, the direction of elementary magnets are regular. In bodies that are easly made magnets, the composition of the elementary magnets can be arranged through the process to make a magnet, while the elementary magnets of bodies that are difficult to change to magnets are difficult to be arranged. When a magnet is heated or hit, the composition of the elementary magnet becomes irregular, so the magnetic property is lost. 

Reference:
Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

Magnetism Theory

Theory of magnetism is divided into two of them

1. Magnetism Theory: Based on magnetism theory, if a magnet is divided into small pieces, the pieces remain magnetic, and still have the north and the south poles, so a magnet consists of tiny magnets which are called elementary magnets. Bodies such as iron, steel, and several other metals are ferromagnetic bodies, that as we know are materials which are easly attracted by magnets. In bodies which have not become magnets, the composition of the elementary magnets is not in order. If the ferromagnetic bodies lie in a magnetic field, the bodies will be induced, so the elementary magnets will rotate to arrange themselves (they arrange themselves in parallel to magnetic poles exerted from the outside). When the elementary magnets have been arranged, the bodies will become magnets.
2. Earth Magnetism Theory: A physicist named William Gilbert (1544-1603) proposed that the earth is a giant magnet. The earth is a natural magnet. The north pole of earth magnet lies on the south pole of earth and the south pole of earth magnet lies on the north pole of the earth. Hence, a compass’s needle always points to the north and south directions, and the north pole of compass needle points to the north pole of earth because it undergoes an attractive force against the south pole of earth magnet which lies on the north pole of earth, while the south pole of compass needle points to the south pole of earth because is undergoes an attractive force against the north pole of earth magnet on the north pole of earth. Study the figure 

From the figure, obviously the magnet axes or magnetic poles of the earth do not coincide with the rotational axic or earth’s poles. The magnitude of declination angle between them is 15o. Hence, the location (direction) of compass needle does not precisely show the direction of the north and south of poles of the earth. The declination magnitude of compass needle direction in every place of earth is not equal. The closer to the equator, the smaller the declination. This declination angle is called the angle of declination.

Reference:
Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

Electric Charge

belajar.kemdikbud.go.id

All matters in this universe are made up of very small atoms. The atoms consist of particles that are positively, negatively, and neutrally charged. Positive charge is called proton, negative charge is called electron, and neutral charge is called neutron.

An atomic nucleus consists of protons and neutrons surrounded by electrons that move continuously. Electrons in the atom can escape or enter into the composition of an atom. If the electrons escape from the composition of an atom, the number protons in the atom is more than the number of electrons, so the atom becomes positively charged. Meanwhile, if the electrons enter to the composition of an atom, the number of protons in the atom is less than the number of electrons, so the atom becomes negatively charged. The atom will have neutral property (uncharged) if the number of protons in the atomic nucleus is equal to the number of electrons that revolve around the atomic nucleus.

It can be concluded that a neutral body can be statically charged by rubbing it. Another example is when a plastic rod is rubbed with a wool, the electrons from the wool move to the plastic rod, so the plastic rod ha excessive electrons. Hence, the plastic rod becomes negatively charged. On the contrary, when a glass rod is rubbed with silk electrons from the glass rod move to the silk, so the glass rod lacks electrons. Accordingly, the glass rod becomes positively charged.

Table The Mass and Charge of Electrons, Protons, and Neutrons.

Reference:
Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

Magnetic Materials and Magnetic Properties

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

1. Ferromagnetic bodies, namely bodies which are strongly attracted by magnets.
2. Paramagnetic bodies are bodies which are weakly attracted by magnets. For examples, aluminium, magnesium, platinum, and manganese.
3. Diamagnetic bodies are bodies which are not attracted or even tend to be repulsed by magnets. For examples, bismuth, pure zinc, lead, gold, silver, and copper.

Ferromagnetic bodies are widely used as magnets because their magnetic property does not easily disappear, mainly in steel. Meanwhile, based on the ability to store the magnetic property, magnets can be grouped into permanent and nonpermanent magnets.

1. Permanent Magnets :Iron, steel alloys, nickel and cobalt are hard metals which are difficult to change to magnets. But, after they become magnets, those metals are able to store their magnetic property for a long time. This ability makes hard metals widely used as magnets. Magnets which are able to store their magnetic property for a long time are called permanent magnets. Permanent magnets are used in an ammeter, voltmeter, cassette tape, disk, and loud speaker.
2. Nonpermanent Magnets: Bodies that are not included into hard metals are easily made magnets but they also easily lose their magnetic property. (That kind of bodies is called “soft metal”, eventhough there is no metal that is really soft). Magnets which are made of soft metal are called soft magnets (nonpermanent magnets). One of the examples of nonpermanent magnets is soft iron. The soft iron that is conducted by electric current can change to magnets, but when the electric current is turned off, its magnetic property will disappear. (The method to make magnets by electric current will be studied later).

Reference:

Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More

Subtances are divided into 3 kinds

Artikelku kodong friends it we know that substances have different resistance. It shows that the ability of substances in conducting an electric current is different from one another.

Based on the conductivity, subtances are divided into 3 kinds, those are conductors, semiconductors, and insulators.

1. Conductors : Aconductor is a material or substance that easily conducts an electric current and is easily conducted with an electric current. The conductor materials and substances, among others, are iron, copper, aluminum, graphite, and steel.
2. Semiconductors : A semiconductor is amaterial or substance the elecrtric conductivity of which lies between conductor and insulator. In other words, a semiconductor is a material or substance that sometimes acts as a conductor and sometime acts as an insulator. The semiconductor materials or substances, among others, are germanium, gallium, arsenic, and silicon. In semiconductor materials, the electric conductivity will be better, if the temperature is higher. At a high temperature, electrons that first are bonded by atomic nucleus will vibrate and have energy to escape themselves from their bond with atomic nucleus. That causes the number of free electron to be larger, so the electric current that flows is larger.
3. Insulators : An insulator is a material or substance that is difficult to conduct an electric current or is not easily conducted with an electric current. The insulator materials or subtances, among others, are glass, wood, plastic, and rubber.

Reference:

Irawan, Etsa Indra dan Sunardi. 2008. Pelajaran IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.

Read More