f.
Calculate (a) the impedance, (b) the current, (c) the p.f.
For (a):
Z X
Z
2
2 2
( )
(9 (12 15
Ω
∴ Ω
For (b):
I
V
Z
I
(A)
150 V
15
10A
∴
Ω
For (c):
p.c.6 750 W
φ
∴
Example 2
A capacitor reactance 12Ω connected series with resistor across 150V supply.f.f.
Calculate (a) the impedance the circuit, (b) the current, (c) the p., and (d) the power.Baisc Electrical Installation Work
202
In a. cos
p.f.f.
30
50
0.
For (a):
Z X
Z
2
2 2
( )
(30 (40 50
Ω
∴ Ω
For (b):
I
V
Z
I
(A)
250 V
50
5 A
∴
Ω
For (c):
p. circuit the power consumed given the product the cur-
rent and that part the voltage which phase with the current. cos
p., and (d) the power. The
in-phase component the voltage given cosφ, and power can
also given the equation:
P VI
cos (W)
φ
Example 1
A coil has resistance 30Ω and reactance 40Ω when connected 250V supply.6 leading
φ
R
Z
∴
Ω
Ω
.6 lagging
φ
R
Z
∴
Ω
Ω
For (d):
P VI
P
cos (W)
250 0.
9
15
0
