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Power
Dissipation in Resistors
When an electric current passes through a conductor, some useful
electrical energy is dissipated in the form of heat EXPRESSION
FOR POWER LOSS Let
'q' amount of electric charge passes through a conductor in unit
time, the electric current through the conductor is given by: I
= q/t Or q
= I x t ............... (1) During the flow of electric current energy lost in the form
of heat is equal to q x V, where V is the potential
difference across the ends of conductor. Energy
lost = q x
V Putting
the value of q, we get Energy
lost = I x
t x V But
Energy /t = Power
POWER LOSS
IN TERMS OF CURRENT AND RESISTANCE According
to Ohm's law V = IR. putting the value of V, we get Power = (IR)I
POWER LOSS
IN TERMS OF RESISTANCE AND POTENTIAL DIFFERENCE As
power = VI and according to Ohm's law I = V/R, putting the value of i, we get Power
= VI
UNIT
OF POWER In SI
system unit of power is Watt. |
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energy. This loss of electrical energy is due to the collision of
charges with the atoms of conductor. Loss of electrical energy in unit
time is referred to as "power dissipation in resistor".