1) A current of 5 A flows through a non-inductive resistance connected in series with a
chocking coil when a voltage of 230 V,50 Hz is applied across it. If the voltage across
the resistance is 115V and that across the chocking coil is 184V,calculate?
Answers
Answer:
Voltage...............................
Answer:
As seen from the vector diagram of Fig. . BC2 + CD2 = 2002 ...
(i) (125 + BC)2 + CD2 = 2502 ..
.(ii) Subtracting Eq. (i) from (ii), we get,
(125 + BC)2 − BC2 = 2502 − 2002 ∴ BC = 27.5V;
CD = √(2002 - 27.52) = 198.1V
(i) Coil impedance = 200/5 = 40 Ω
VR = IR = BC or 5 R = 27.5 ∴ Ρ = 27.5/5 = 5.5 Ω
Also VL = I . XL = CD = 198.1 ∴ XL = 198.1/5 = 39.62 Ω or XL = (402 - 5.52) = 39.62Ω
(ii) Power absorbed by the coil is = I2R = 52 × 5.5 = 137.5 W Also P = 200 × 5 × 27.5/200 = 137.5 W
(iii) Total power = VI cos φ = 250 × 5 × AC/AD = 250 × 5 × 152.5/250 = 762.5 W
The power may also be calculated by using I2R formula.
Series resistance = 125/5 = 25Ω
Total circuit resistance = 25 + 5.5 = 30.5 Ω
∴ Total power = 52 × 30.5 = 762.5 W