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Universitas Jenderal Soedirman
Purwokerto
FISIKA DASAR II
Oleh :
Mukhtar Effendi
Universitas Jenderal Soedirman
Purwokerto
Mukhtar Effendi
Ilmu Fisika
2
Universitas Jenderal Soedirman
Purwokerto
Coulomb’s Law
Mukhtar Effendi
Ilmu Fisika
3
Universitas Jenderal Soedirman
Purwokerto
The electron and proton of a hydrogen atom are separated (on
the average) by a distance of approximately 5.3 x 10-11 m. Find
the magnitudes of the electric force between the two particles.
Elektron dan proton atom hidrogen terpisah (secara ratarata) sejauh 5,3 x 10-11 m. Hitunglah besarnya gaya listrik
antara dua partikel tersebut.
Mukhtar Effendi
Ilmu Fisika
4
Universitas Jenderal Soedirman
Purwokerto
Consider three point charges located at the corners of a right triangle
as shown below, where q1 = q3 = 5.0 C, q2 = -2.0 C, and a = 0.10
m. Find the resultant force exerted on q3.
Terdapat tiga buah muatan titik yang terletak pada titik sudut segitiga
sebagaimana terlihat pada gambar, yang q1=q3= 5 C, q2= -2 C dan a =
0,1 m. Hitunglah resultan gaya yang dialami oleh q3.
Mukhtar Effendi
Ilmu Fisika
5
Universitas Jenderal Soedirman
Purwokerto
The Electric Field
the electric field vector E at a point
in space is defined as the electric
force Fe acting on a positive test
charge q0 placed at that point
divided by the test charge:
Mukhtar Effendi
Ilmu Fisika
6
Universitas Jenderal Soedirman
Purwokerto
A charge q1 = 7.0 C is located at the origin, and a second charge q2
= -5.0 C is located on the x axis, 0.30 m from the origin. Find the
electric field at the point P, which has coordinates (0, 0.40) m.
Mukhtar Effendi
Ilmu Fisika
7
Universitas Jenderal Soedirman
Purwokerto
Hukum Gauss
Mukhtar Effendi
Ilmu Fisika
8
Universitas Jenderal Soedirman
Purwokerto
the electric potential created by a point charge at any distance r
from the charge is
the potential energy of the system
Obtaining the Value of the Electric Field from the Electric
Potential
Mukhtar Effendi
Ilmu Fisika
9
Universitas Jenderal Soedirman
Purwokerto
A proton is released from rest in a uniform electric field that has a magnitude of 8.0
x 104 V/m. The proton undergoes a displacement of 0.50 m in the direction of E.
(A) Find the change in electric potential between
points A and B.
(B) Find the change in
potential energy of the
proton–field system for
this displacement.
(C) Find the speed of the proton after
completing the 0.50 m displacement
in the electric field.
Mukhtar Effendi
Ilmu Fisika
10
Universitas Jenderal Soedirman
Purwokerto
An electric dipole consists of two charges of equal magnitude and
opposite sign separated by a distance 2a, as shown in Figure
below. The dipole is along the x axis and is centered at the origin.
(A) Calculate the electric potential at point P.
(B) Calculate V and Ex at a point
far from the dipole.
Mukhtar Effendi
Ilmu Fisika
11
Universitas Jenderal Soedirman
Purwokerto
(C) Calculate V and Ex if point P is located anywhere
between the two charges.
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Ilmu Fisika
12
Universitas Jenderal Soedirman
Purwokerto
capacitor
Mukhtar Effendi
Ilmu Fisika
13
Universitas Jenderal Soedirman
Purwokerto
A parallel-plate capacitor with air between the plates has an
area A = 2.00 x 104 m2 and a plate separation d = 1.00 mm.
Find its capacitance.
Mukhtar Effendi
Ilmu Fisika
14
Universitas Jenderal Soedirman
Purwokerto
Combinations of Capacitors
Mukhtar Effendi
Ilmu Fisika
15
Universitas Jenderal Soedirman
Purwokerto
Capacitors with Dielectrics
A charged capacitor (a) before and (b) after insertion of a dielectric between the
plates. The charge on the plates remains unchanged, but the potential difference
decreases from V0 to V= V0/. Thus, the capacitance increases from C0 to  C0.
Mukhtar Effendi
Ilmu Fisika
16
Universitas Jenderal Soedirman
Purwokerto
A parallel-plate capacitor has plates of dimensions 2.0 cm by
3.0 cm separated by a 1.0-mm thickness of paper (= 3.7).
Mukhtar Effendi
Ilmu Fisika
17