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MUATAN LISTRIK

HUKUM COULOMB

Mata Kuliah

Fisika Dasar II

Jurusan Fisika FMIPA

Universitas Brawijaya

2015

LISTRIK

Petir

merupakan

salah satu

contoh

fenomena

yang

berkaitan

dengan listrik.

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MATERI & ATOM

Semua materi terbentuk dari atom-atom

Padat Cairan Gas

STRUKTUR ATOM

Bagian atom : nukleus dan elektron.

Bagian nukleus : proton dan neutron.

Elektron bermuatan listrik negatif.

Proton bermuatan listrik positif .

Neutron tidak bermuatan listrik.

Proton

Electron

Neutron

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STRUKTUR ATOM

Nomor Atom (Z)

Banyaknya elektron= Z.

Banyaknya proton=Z.

Nomor Masa Atom (A)

A=Z+N (Neutron).

Ukuran

Diameter atom sekitar 10-10 m.

MUATAN LISTRIK

Satuan muatan listrik (Q) adalah Coulomb.

Macam muatan listrik : positif dan negatif.

Muatan elektron = -e = -1.60 x 10-19 C.

Muatan proton = +e = 1.60 x 10-19 C.

Keadaan normal atom adalah netral (tidak bermuatan).

Nukleus berat, elektron ringan. Muatan biasanya dibawa

oleh elektron.

Saat mendapatkan (kelebihan) elektron, benda akan

bermuatan negatif (Q=-Ne).

Saat kehilangan (kekurangan) elektron, benda akan

bermuatan positif (Q=+Ne).

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MUATAN LISTRIK

Gaya pada muatan

Muatan sejenis tolak

menolak.

Muatan tidak sejenis tarik

menarik.

MUATAN LISTRIK

TONGKAT PLASTIK yang

digosok dengan kain wol

atau bulu akan menjadi

bermuatan negatif.

TONGKAT GELAS yang

digosok dengan kain sutra

akan menjadi bermuatan

positif.

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KEKEKALAN MUATAN LISTRIK

Muatan listrik tidak dapat diciptakan atau dimusnahkan.

Muatan listrik dapat dipisahkan atau dipindahkan.

Contoh,

Bila plastik dan wol (pada keadaan awal ) masing-masing tidak

bermuatan, maka setelah digosok:

Muatanplastik= - Muatanwol.

ISOLATOR dan KONDUKTOR

Jika konduktor diberi muatan,

semua muatan akan berada di

bagian permukaan/luar (tidak ada

yang berada di dalam).

Jika isolator diberi muatan,

muatan mungkin berada (atau

tidak berada) di bagian dalam.

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ISOLATOR dan KONDUKTOR

Conductors cannot be charged by

friction.

However, charge can be transferred

to a conductor by contact with a

charged object.

The charges arriving at the

conductor

stay on the outer surface and

distribute

themselves over that surface so

that they are as far away from the

forces of the other charges as

possible.

ISOLATOR dan KONDUKTOR

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ISOLATOR dan KONDUKTOR

In insulators, the electrons are tightly bound in the

atoms and are not free to move around. When

insulators are charged, e.g. by friction, patches of

molecular ions are created on the surface, but these

patches are immobile.

In solid metal conductors, the outer (valence)

electrons of the atoms are only weakly bound and are

free to move around in the solid. The conductor as a

whole may be electrically neutral, but the electrons are

rather like an electrically charged liquid, a sea of

electrons within the material. Electrons are the

charge carriers.

There are other forms of conduction (in

semiconductors, ionic

liquids, etc.) in which the charge carriers are not

electrons.

LOGAM dan KONDUKSI

Notice that metals are not only good electrical conductors, but they are

also good heat conductors, tend to be shiny (if polished), and are maleable

(can be bent or shaped).

These are all properties that come from the ability of electrons to move

easily.

Path of electron

in a metal

This iron atom (26 protons, 26 electrons) has two

electrons in its outer shell, which can move from

one iron atom to the next in a metal.

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ELECTROSCOPE

PELEPASAN MUATAN

The human body, composed mainly

of salty water, is a moderately good

conductor.

Therefore, a person touching a

charged object will normally

discharge the object.

Where the charge goes next

depends on the degree to which

the person is insulated form ground

(e.g., by rubber shoe soles).

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POLARISASI MUATAN

MUATAN DAN INDUKSI

By using charge

polarization,

it is possible to induce

charge on an electrically

neutral object.

Example: Bring a charged

rod near (but not

touching) an electroscope

and observe the effect on

the leaves.

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MUATAN DAN GAYA

SIFAT MUATAN

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HUKUM COULOMB

HUKUM COULOMB

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HUKUM COULOMB

PENGGUNAAN HUKUM COULOMB

1. Coulombs Law applies only to point charges. (This is

particularly important because charge tends to move round

on conductors.)

2. Strictly speaking, Coulombs Law applies only to

electrostatics (non-moving charges). (However, it is usually

OK provided v

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Force of One Charge on Another

Resultant of Two Electric Forces on a Charge

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Resultant of Two Electric Forces on a Charge