ELECTROTECHNOLOGY
ELTK1200
REVIEW #2
1.
A 80 6 resistor is connected in series with a 0.2H practical inductor. The resultant
phase angle of the circuit is 30° when connected to a 50 Hz. supply. Calculate RAC
for the coil if RDC is 10 6 (RAC = 18.776).
2.
Calculate R and C for the following circuit (R = 1006, C = 42.46F).
3.
For a series circuit consisting of a 1000 6 resistor and a 10 F capacitor connected
to a 120 V, 60 Hz supply. Calculate;
(a)
Real Power (P = 13.5W).
(b)
Reactive Power (QC = 3.57VAR).
(c)
Apparent Power (S = 13.9V#A).
(d)
Power Factor (pf = 0.967 leading).
4.
A 200V, 50 Hz source is connected to a RLC series circuit consisting of a 100 6
resistor, 8 H inductor and 1 F capacitor. Calculate;
(a)
Impedance (Z = 6776).
(b)
Current (I = 295.3mA).
(c)
Phase Angle ( = 81.5° leading).
(d)
Voltage across the inductor, VL (VL = 742.2V).
5.
Two capacitors are constructed using the same dielectric material and have the same
value of capacitance. The first capacitor has a distance between the plates of
0.02mm and a plate area of 0.12cm2. If the second capacitor has a plate area of
0.21cm2, determine the distance between the plates (d = 0.035mm).
6.
A 12H choke (practical inductor) draws 10mA when connected to a 10V DC source.
When the choke is connected to a 125V, 50Hz source, the current is 20mA.
Calculate:
(a)
The AC resistance of the choke (RAC = 39856).
(b)
The Q-factor of the choke (Q-factor = 0.756 ).
(c)
The circuit phase angle ( = 37.1° lagging).
ELTK1200
Marine Institute
Rev 2
133
7.
The series circuit shown below has an impedance of Z = 10006, a phase angle of
= 30°, and the inductive reactive power is 10 VARs. Find:
(a)
Resistance and total inductive reactance of the circuit
(R = 8666, XL = 5006).
(b)
Frequency and voltage of the source, VS (f = 212.2Hz, VS = 141.4V ).
8.
The instantaneous value of the voltage and current for a series RLC circuit is 16.77V
and -93mA at 6ms. If the frequency is 90Hz, the power factor is 0.917 leading and
XC = 2 XL. Determine R, L and C (R = 2606, L = 200mH, C = 7.82F).
(VS = 75.0V, I = 264.4mA)
Hint: Current is the reference.
ELTK1200
Marine Institute
Rev 2
134