Page 165 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

In this also the case power is positive so it is shown in the upper half of the cycle. This is true only for resistive
circuit.
W = I R
2
Cos ф = R/Z (R = Z )

R/Z = 1
Now power factor of the resistive circuit is one and there for it is phase angle is one
Power developed = V x I
AC Circuit containing pure inductance only

Inductance circuit there is no resistance and capacitance
Apure inductance is a coil wounded on a laminated iron core with a few turns of thick wire . If an AC voltage ‘V ‘
is applied across such a circuit a current will flow through it .The magnitude of the current is given by
I = V/Z Z = XL
V/XL = I
XL = 2πfL
XL = inductive reactance

A pure inductive circuit current not in phase with voltage by 900 electrical
W = V X I X Cosф
Cos ф = R/Z R = 0
Hence W = V I cosф

= Vx Ix 0 = 0
In pure inductive circuit value of resistance is zero, there is no resistive potential drop in the circuit hence the
power developed is zero
AC Circuit containing pure capacitance only

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CITS : Power - Electrician & Wireman - Lesson 26-29