01 muatan listrik fisika ii
DESCRIPTION
materi perkuliahan untuk jurusan fisika semester 2TRANSCRIPT
-
3/12/2015
1
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.
-
3/12/2015
2
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
-
3/12/2015
3
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).
-
3/12/2015
4
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.
-
3/12/2015
5
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.
-
3/12/2015
6
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
-
3/12/2015
7
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.
-
3/12/2015
8
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).
-
3/12/2015
9
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.
-
3/12/2015
10
MUATAN DAN GAYA
SIFAT MUATAN
-
3/12/2015
11
HUKUM COULOMB
HUKUM COULOMB
-
3/12/2015
12
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
-
3/12/2015
13
Force of One Charge on Another
Resultant of Two Electric Forces on a Charge
-
3/12/2015
14
Resultant of Two Electric Forces on a Charge