Download Elektrostatika: Hukum Coulomb

Electrostatic:
Electric Potential
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Chapter 24 Halliday-Resnick 9th Ed.
Electric potential energy:


An Electric force act between two or more particles
Assign an Electric Potential Energy to the system
initial ( )
Change of states
Δ =
−
=−
final ( )
Conservative force → path independent
Reference:

= infinite separation →
=0

= neighboring particles →
=
= ΔU = −
Work done by
the force during
move from ∞
Electric Potential:
Δ =
=
−
=−
[J/C] (scalar)
=
=0
=
−
=−
[volt (V)]
Work done by
the force during
move from ∞
Calculating
=
−
=
∙
=
∙
=−
=−
=0
=
∙
∙
∙
from
Potential due to a Point Charge
Move from to infinity
∙
= cos
− = −∫
∙
;
= 0; =
1
=
0−
=
=
1
=−
1
+
−
=−
1
1
→ +
→ −
Potential due to a System of
Point Charge
=
Potential due to a continuous
charge distribution:
Line of charge
=
=
ln
=
= /
=
=
+
+
/
Potential due to a continuous
charge distribution:
charged disk
=
=
=
=
=
=
=
+
+
−
Calculating the Field from the Potential
a positive test charge
moves through a
displacement
from one equipotential
surface to the adjacent surface.
the work the electric field does on the test
charge during the move is
=−
=
=−
=−
=−
=−
The figure shows three pairs of parallel plates with the same
separation, and the electric potential of each plate. The electric field
between the plates is uniform and perpendicular to the plates.
(a) Rank the pairs according to the magnitude of the electric field
between the plates, greatest first. 2,1-3
(b) For which pair is the electric field pointing rightward? 3
(c) If an electron is released midway between the third pair of plates,
does it remain there, move rightward at constant speed, move
leftward at constant speed, accelerate rightward, or accelerate
leftward? accelerate leftward
Electric Potential Energy of a System of Point Charges
The electric potential energy of a system of fixed
point charges is equal to the work that must be
done by an external agent to assemble the system,
bringing each charge in from an infinite distance.
=
What is the electric
potential energy of this
system of charges? Assume
that = 2
and that
ql = +3 nC,
q2 = -2 nC
q3 = +5 nC,
Potential of a Charged Isolated
Conductor
−
=−
∙
= 0, inside the conductor
− =0
=