OHM'S LAW

OHM'S LAW

OHM'S LAW IS A A LAW WHEN THE FLOW OF CURRENTS WAS DISCOVERED BY G.S OHM IN 1828, A PHYSICAL MECHANISM WAS RESPONSIBLE FOR THE FLOW OF CURRENTS TO BE DISCOVERED.

OHM'S LAW STATE THAT, V = IR, WHERE THE CONSTANT OF PROPORTIONALITY R IS CALLED RESISTANCE OF THE CONDUCTOR. THE SI UNITS OF RESISTANCE R IS NOT ONLY DEPEND ON THE CONDUCTOR.

# CONSIDER A CONDUCTOR SATISFYING EQUATION OF OHM'S LAW V = IR TO BE IN THE FORM OF A SLAB OF LENGTH l AND CROSS-SECTIONAL A. IMAGINE PLACING TWO SUCH IDENTICAL SLABS SIDE BY SIDE, SO THAT THE LENGTH OF THE COMBINATION IS 2l. THE CURRENT FLOWING THROUGH THE COMBINATION IS THE SAME AS THE FLOWING THROUGH EITHER OF THE SLABS. IF V IS THE POTENTIAL DIFFERENCE ACROSS THE ENDS OF THE FIRST SLAB, THEN V IS ALSO A POTENTIAL DIFFERENCE ACROSS THE ENDS OF THE SECOND SLAB SINCE THE SECOND SLAB IS IDENTICAL TO THE FIRST AND THE SAME CURRENT I FLOW THROUGH BOTH. THE POTENTIAL DIFFERENCE ACROSS THE END OF THE COMBINATION IS CLEARLY SOME OF THE POTENTIAL DIFFERENCE ACROSS THE 2 INDIVIDUAL SLABS AND HENCE EQUAL 2V. THE CURRENT THROUGH THE COMBINATION IS 1 AND THE RESISTANCE OF THE COMBINATION Rc.

                                                          Rc = 2V/I = 2R

SINCE V/I= R THE RESISTANCE OF EITHER OF THE SLABS. THUS DOUBLING THE LENGTH OF A CONDUCTOR DOUBLES THE RESISTANCE. IN GENERAL, THEN RESISTANCE IS PROPORTIONAL TO LENGTH.