Ohm’s law: It states that, the electrical current
flowing through a conductor material is directly proportional to the voltage
difference between the ends of the conductor material, keeping the physical
conditions unaltered.
So,
I proportional to V
Where, I= electric current flowing
through conductor material,
V= voltage difference between
the ends of the conductor material.
Or,
V/I=constant
This constant is known as resistance of
the conductor material and is denoted by `R’.
Law
of Resistance: This law states that the resistance of
a conductor material is directly proportional to the length of the conductor,
inversely proportional to the cross-section of the conductor and depends upon
the nature of the conductor material at constant temperature.
Now we can say that, R =p. l/a
Where R = resistance of the
conductor material
l = length of
the conductor material
a=
cross-section area of the conductor material
p=
specific resistance or resistivity of the conductor material.
Kirchoff’s
law: When the electrical networks cannot be
solved by ohm’s law, then we take help to different laws and theorem to save
time and to reduce mathematical calculations.
Kirchoff’s laws comprise of two laws: (1)
Current or point law and (2) Voltage or mesh law.
Current or point law:
It states that the algebraic sum of the currents meeting at a point in an
electrical circuit is always zero.
This law proves that
the incoming current = outgoing current
Voltage or mesh law:
It states that, in any closed part of an electric circuit, the algebraic sum of
the E.M.F is equal to the algebraic sum of the products of the resistances and
currents flowing through them.
Coulomb’s
law: The electric force attraction or
repulsion between two point charges is directly proportional to the product of
two charges and inversely proportional to the square of the distance between
them. The force acts along the line joining the two charges and its value depends
upon the nature of the intervening medium.
Explain: Let us consider two point
charges q₁ and q₂ separated by a distance r, then from Coulomb’s law, the
electric force F between the two charges in vacuum is given by,
F proportional q₁. q₂/r²
Where ε₀ be the permittivity of vacuum
Where 1/4 π ε₀ = 9×10⁹ Nm²C⁻²