FUNDAMENTALS& BASIC THOERY

POWER:



Power is defined as the rate of doing work. The electrical unit of power (P) is the Watt(W). With steady current as with d.c



1W= 1Vx1A



or W=VA



in symbols P = VxI. 1KW= 1000Watts.







ENERGY:



Energy is defined as powerxTime



(i.e) Electrical energy = VIt, where t is time in seconds. The unit is joules which is equivelent to 1 ampere at 1 volt for 1 second.



The practical unit of Energy is the kilowatt hour .



Kwh= watts x hours/1000



Energy loss in Resistance:



If current ' I ' is passedthrough resistance 'R'nthen the voltage drop across the resistance will be



V=IR



The watts used wil lbe VI, Therefore, the power in the circuit will be


P=VI=(IR) x I =I²R

I²R is usually known as the copper loss or the I²R loss.