example one :
MC >MC
·
-
8 MC 4 -
in i
A
40 cm
B
20 cm
C F S
STATTIK ELECTIRIICIIITY a) draw free
body diagram of forces acting on 4MC charge
y
&
electric charge (a) - - -
4 MC
>
attraction ((unlike) repulsion (2 like)
the charge of an object will be a multiple of elementary charge SMC 4UC charge 4UC charge
*
Force of 6 MC
> :
Force of -
on on
& =
Number of electrons (or protons) x 1
,
6 X18
+
C
b) calculate electrostatic force of SNIC charge on 4MC charge .
· charge of electron elemen a se F =
1991
= (9x189)(8x10 %)4x10) = 1
, 8N attraction to the left
hollow sphere
↳
(48x18-2)2
units
her
:
negatively charged
c) calculate electrostatic force of JNIC charge on the 4MC charge . positively charged
MilliCoulomb : 1mc = 1 x 153(
10 C
= =
19 : 9 =
1909(6x10
% (4X103) =
5 4N attraction to the right
IMC
,
microCoulomb : =
1 x
- + + + + + + + + +
10- 2)
p
(20 x
nanocoulomb Inc =
1 x15
*
C electric feild between oppositely charged
d) determine the 4 MC charge .
:
net force acting on the
---
-----
parallel plates
= ,g
*
plcCoulomb :
(p)
=
1 X15 C Free -
=
3 6N to the right
,
electrostatic forces two
---------
example :
↳ occur between objects which are charged like charges repel 9, =
18MC electric feild strength (E)
-
,
- 7
as find electrostatic force of at due to al
i
and unlike charges attract
(9x189)(18x10 -)(12x18) the magnitude of the electric feild strength is defined as the
3m gres F =
May =
>
E
S·
F 93
= -
45MC
r2
0 , 216N upwards
(3)2 force (f) per unit positive charge
like charges repel -
+
- - - - - - -
=
pon a
&estaforexpriencedbucharge
at that
12m)s
=
92 +
3m
=
[
find net force on a
C)
b) find electrostatic force on ge duetoas
Fnet" =
(0 , 216) + (0 54)2,
(9x189)(45x10 6)(12x18
F
F (N C")
F
attract electric feild strength at that point
unlike charges F ka
.
=
=
Fret =
0
, 582N
r2 (3)2
Coulomb's Law =
0 . 54N to the right tano- : 0 =
21 ,
80
above
horizonal
electric field strength due to a point charge
> definition :
Two point charges in free space or air exert forces on > electric field strength decreases as distance from charge increases
eachother . The force is directly proportional to the product of the electric field lines (more lines closer together =
stronger) Coulomb's constant
>
-
1 C .
· area
charges and inversely proportional to the square of the distance electric field :
A region of space in which an electric charge experiences
I
7
responsible for
91 92
between the charges r a force
-[ > +
t test charge
marix
+ electric
test charge
strength
7
Feild
(N C") too (m)
=
.
:
(f
92 -A
91
F
.
=
k 1. electric fella strength is
inversely proportional to the square of distance from
distance between
rz point charge a (EC)
Mi
electrostatic
point charges (m)
>
-
force (N)
electric feld due to a
2 Charge a is responsible for electric feild Increasing charge a will increase
fold due
.
to a negative
.
electric
Coulomb's constant (9x10 9 N .
m ? c") positive point charge
the felld strength
point charge