Current Carriers :

   The charged particles whose flow in a definite direction constitues the electric current. eg. electrons in conductors, ions in electrolyte, electrons and holes in semi-conductor.
Electromotive Force  of a cell is defined as the maximum potential difference between the two electrodes of a cell when the cell is in the open circuit. EM.F. of a cell depends upon the nature of electrodes, nature and concentration of electrolyte used in the cell and its temparature.
Electric Current :

 The flow of charge in a definite direction.

S.I unit is Ampere.current is a Scalar.
Drift Velocity :

  Avg velocity with which free electrons get drifted towards the positive end of the conductor under the influence of an external electric field. Drift velocity of ellectrons is given by...
                        v_d = - eE/m
where e is the charge on electron, m is the mass, E is the electric field applied and is the time of relaxation.
value of drift velocity is about 10^-5 m/sec

 

I = nAev_d = nAeE_e

n is electron density

 

            V proportional to I

R  is known as Resistance........Si unit is Ohm...

 

R is given by....

 

       R = ml / (ne²A) =  l / A

 is called resistivity or specific resistance...

 = m / (ne²)

 

   Amount of current flowing per unit area of cross section of the conductor, provided area is held in a direction perpendicular to the direction of current.

                        J = I / A = nev_d

SI unit is Am^-2

 

 

       R_{t 2} = R_t1[ 1 + (t₂ - t₁) ]

 

R_s = R₁ + R₂ + R₃ +...........

 

1/R_p = 1/R₁ + 1/R₂ + 1/R₃ +...........

 

     V =  - Ir

or

     r  = (  - V ) / I

        = (  - V )R / V

 

Self-written hope it will be usefull.....

 

more editions coming..........