OHM'S LAW andJOULE'S LAW

OHM'S LAW





INTRODUCTION



Ohm’s law is a quantitative relation b/w potential difference and electric current.





STATEMENT

According to Ohm’s law,

"The electric current passes through a conductor is directly proportional

to the potential differences between the ends of conductor,

if physical conditions of conductor remain constant."

i.e.

IV

I = kV

K =constant and is called "conductivity of material"

I/K = V

or

V = I/K

V = I x 1/K

Let [1/K = resistance]

V=IxR









GRAPHICAL REPRESENTATION









JOULE'S LAW

INTRODUCTION:

When an electric current passes through a wire heat energy is produced. It is due

to the collision of electrons with the atoms. In order to continue steady current,

work has to be done on electric charges. STATEMENT:

Amount of work done on electric charge on steady current is directly proportional

to amount of heat.

Work Heat

PROOF: Consider a conductor through which electric current q is passing in

time t let the potential difference between two ends of wire is V. We know that

v = W/q

or

W = q x V_(i)

According to Ohm’s law V = IR

putting the value of V in equation (i)

W = q x IR_______(ii)

But

I = q/t

Or

Q = It

putting the value of q in equation (ii)

W = It . IR

W = I2Rt