12th Physics, Chapter 12th, Punjab text Book

3. OVERVIEW
 Electrostatics
 Charge
 Electric force
 Coulomb law
 Mathematical form
 Vector form

6. ELECTRIC FORCE
The force that holds positive and negative
charges that make up atoms and
molecules is called electric force.

7. Between Two Point Charges
There Is Force Of Attraction Or
Repulsion Depending Upon the
Nature Of Charges.
Fig. Understanding Of Attraction And Repulsion
COULOMB’S LAW STATEMENT
Charles Augustine de Coulomb

9. Coulomb Showed That:
1)F Q1Q2
2)F
1
3)The Magnitude Of the Force Depends on
the Medium.
 By Combining Two Equations We Get,
Q1Q2
R2
F
 Using Proportionality K We Get,
R
2

10. 12
C 2
/ Nm 2
10ℇ0 = 8.84
0
4
1 1 2
R 2
Q Q
F
Then the Force is Given by following equation:
LIMITATIONS
1.The charges to be considered are Point Charge.
2.They Should Be Stationary With Each Other.
N
The Constant Of Proportionality Is Given By:
 K = 1
N

11. COULOMB’S LAW IN VECTOR FORM
Force on Q1 is given by
F21 = 12
0
4
1 2
R12
2
1 Q Q
r^ F12 =
0
4
1
r21
1 2
R21
2
Q Q
^
Force on Q2 is given by
,We Can Write