ELECTRIC CELL AND EMF

A source of electric energy

EMF-electromotive force:-

It is the workdone by a cell in forcing a unit positive charge to flow through the whole circuit.

EMF (E)=dw/dq

UNIT OF EMF is volt(V)

 A battery of emf  and internal resistance  connected to a load resistor of resistance .

INTERNAL RESISTANCE(r)

It is the resistance offered by the electrolite of the cell to the flow of current through it.

1.it is directly propotional to the seperation between the two plates.

2.it is inversly propotional to the plates area dipped in electrolite.

3.it depends upon nature,concentration,temperature of the electrolite.

   so it increases with increase in concentration.

EQUATION

pottential difference=V

EMF=E

current=i

Internal resistance=r

V=E-i*r

r=(E-V)/i                      [i=V/R]

so

r=(E-V)/(V/R)

then

r=R(E/V-1)      i=E-V/r

E=v+i*r             [V=ir]

E=iR+ir

taking 'i' as common;

E=i(R+r)

so

i=E/(R+r)

  V=E-ir

  E=V+ir

  E=iR+ir

  E=i(R+r)

THEN

  i=E/(R+r)

                                                                                                     by praveen........
                                                                                            if you like it..please comment.