FUNDAMENTALS

FUNDAMENTALS

CURRENT:

The rate at which Electricity flows is termed as "CURRENT". The magnitude of the current deponds upon the electromotive force and also depends upon the nature and dimensions of the path through which it circulates, The steady flow of current is given by the quantity of electricity which passes a given point in one second.

OHM'S LAW:

Ohm's law states that the current in a d.c circuit varies in direct proportion to the voltage and is inversly proportional to the ressistance of the circuit.

(i.e) Current=Electromotive force/resistance

where the units for the above quqntities are ,

current - The Ampere (A)

Electromotive force- the Volt ( V)

Resistance-the Ohm (R)

Ohm's law can be written as, I = V/R or V=I x R

RESISTIVITY:

THe Resistivity of any material is the resitance of a piece of material having unit length and unit sectional area. The symbol is p and the unit is ohm metre. The resistivity of material is not constant but depends on the temperature.

Resistance of a conductor:

The resistance of a uniform conductor with sectional area A and length l is given by,

R = p l /A

The units used must be in millimeters and square millimeters if p is in ohm millimeter units.