Ohm's law And Law of Resistance

Current- 

The electron flow in a circuit is called electric current or the rate of charge flow in a circuit is called current, the current is represented by I. Its unit is ampere and the unit is

The symbol is A. It is measured by ammeter.

Potential Difference - 

The difference in the electrical potentials of any two points in a electric circuit is called potential difference.

or

The work done to move the positive ion from one point to another point the difference between the points is called potential difference.

Its symbol is V and its unit is volt and the volt is represented by V. It is Is measured by voltmeter

Resistance -  

The property of a substance that oppose the current flow in any conductor. It is represented by R and its unit is Ohm and it is expressed by Omega Ω. Ohmmeters are used to measure resistance.

Electromotive Force- The force that acts to accelerate an electron in a substance it is called EMF. It is denoted by E. Its unit is volt and the volt is denoted by V.

Ohm's Law- 

The scientist Georg Simon Ohm established a law regarding the current current and potential and resistance in DC circuits, which is called Ohm's law.
According to this rule - under constant temperature and constant physical conditions, the potential arises at the ends of a resistor in a closed DC circuit is directly proportional to the current flowing through that resistor.
VαI
V = IR
R = V / I

                                            Here-

                                                     R = Resistance in Ω

                                                     V = Voltage in Volt

                                                      I = Current In amp.

Law Of Resistance - 

The resistance of a substance depends on-
1-Resistance of a conductor is proportional to its length- Rαl
2-Resistance of a conductor is inversely proportional to its cross section area - Rα1 / a

3-The resistance of a conductor depends on the nature of the substance.
4- The resistance of a conductor also depends on the temperature. 

Rαl / a 

R = ρ l / a 

Here-

R-conductor resistance in 4
ρ-constant

L-conductor Length cm
a-cross-section area of the conductor in square cm

Specific Resistance - 

The resistance of a unit cubic cm material piece is called its specific resistance. It is denoted by ρ and its unit is Ohm-meter (Ω-m).

Conductance - 

The property of a substance that helps in the flow of current is called conductivity. Conductivity is inversely proportional to resistance. It is represented by G and its unit is Simen or Mho and it is represented by S or Ʊ.

G = 1 / R

Here-

G- Conductivity of conductor in Mho(Ʊ)                                           

R-conductor resistance in Ω

Specific Conductance - 

The opposite effect of specific resistance is called specific conductivity. It is denoted by σ, its unit is Simen per cm.
σ = 1 / ρ

Temp. Coefficient - 

The increase or decrease in the resistance value of a conductor for a temperature change of 1⁰C is called the temperature coefficient of that substance.
If the resistance of the material is R₀ at 0⁰C temperature then Rt at t0
Rt = R0 (1 + α0 t)
α0 = Rt-R0 / R0t
here -
Temp. Coefficient at α0 =0⁰C