Electric force
- It is one of the Example of basic force which is cconservative of nature.
- It can be Negative and positive.
- It follows principle of superposition,it means electric force between two charge particle is independent from prensence or absence of other charge particle.
- Electric force is central in nature.It Means it is exerted along the line,which joins the two points charges.
- Electrostatis force follows Newton's third low.
If Electric force is exerted between two body then it is not nesserary that both bodies will be charge.for example in case of induction the charge body will atract the unchange the body.
Electric repulsion is the confirm test for the presence of charge on two bodies.
Colulombs low
- It is one of the fundamental low of physics.
- It is valid for point charge.
- coulombs low should be applied for charge at rest or very slow moving charge.
Statement of coulombs low
Electric force exerted between two point charges is directly proportional to product of magnitude of two charges and inversely proportional to square of distance between the two charge.
The electric force also depends on the nature of medium presence between the two charges.
Point charge
In this case the total charge is palaced at one point .
Distributed charge system
In this case,charge is distributed through out the system.
|F|∝ |Q1||Q2|...............(1)
|F|∝1/r^2 ...................(2)
From (1) and (2)
|F|∝Q1Q2/r^2
+Q1...................................Q2
F=KQ1Q2/r^2
F=Magnitude of Q1 and Q2 should be force place without sign.
K=Coulomb's constant
K=1/4πt
t= This is electric permibility of medium present between the two charges.
Some important point
- Value of t depends on the nature of medium.
- to = electric permibility of vaccum/air
- t(unit)=c^2/N-m^2
- to =8.85ｘ10^-12 c^2/N-m^2
tr =tm /to
tr =Relativity electric permibility.
tr =Relative E.P
tr =to /to=1 (veccume/air)
tr(water) = 81
tr (organic oil)= 4-50
tr(metels) =∞
tr =It is the unit less and dimension less,also dielectric constant(K)
tr =tm/to
tm = tr . to
K=1/4πt
for medium,
1/4πt =1/4π tr.to
for vaccume/air
K=1/4πto
K=1/4πｘ8.85ｘ10^-12
K=9ｘ10^9 N-m^2/C^2
K= it is not universal constant.
Convertion of Medium Distance into vaccume distance-click here
