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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