I. II. EE 221 (AC CIRCUITS) Midterm Exam 1. Why AC transmission gained favor over DC transmission in the electrical powe

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I Ii Ee 221 Ac Circuits Midterm Exam 1 Why Ac Transmission Gained Favor Over Dc Transmission In The Electrical Powe 1 (127.49 KiB) Viewed 37 times

I. II. EE 221 (AC CIRCUITS) Midterm Exam 1. Why AC transmission gained favor over DC transmission in the electrical power industry? 2. What do you think the reason why inductance is called the electrical inertia? It is a value of a sinusoidal wave in which when applied to a given circuit for a given time, produces the same expenditure of energy when DC is applied to the same circuit for the same interval of time. a. average value b. instantaneous value rms value d. efficient value It is the mean of all instantaneous values of one-half cycle a. average value b. instantaneous value C. rms value d. efficient value It is the ratio of maximum value to the rms value of an alternating quantity. a. Form factor b. Power factor peak factor d. x-factor It is the magnitude of the wave at any instant of time or angle of rotation. a. average value instantaneous value rms value d. efficient value It is the time in seconds needed to produce one cycle. a. period b. full period half period d. peak period Refers to a periodic current, the average value of which over a period is zero. a. Oscillating current b. Periodic current C. alternating current d. instantaneous current It is the maximum value, positive or negative of an alternating quantity. a. average value b. amplitude Discussion Multiple Choice 1. 2. 3. 4. 5. 6. 7. b. sinusoidal value d. transient value It is equal to one-half of a cycle. AC cycle a. b. period frequency C. d. alternation It is the quotient the velocity of propagation and frequency. a. Speed of charges b. speed of light C. wavelength d. speed of current 10. It is the ratio of rms value to the average value of an alternating quantity. a. Form factor b. Power factor C. peak factor d. x-factor 11. It is the ratio of real power to the apparent power of an AC Circuits. a. Form factor b. Power factor c. peak factor d. x-factor 12. What do you mean by a leaky capacitor? a. It's an open capacitor b. It's a shorted capacitor C. It's dielectric resistance has increased d. The fluid used as its dielectric is leaking out 13. A charge body may cause the temporary redistribution of charge on another body without coming in contact with it. How do you call this phenomenon? a. Conduction. b. Potential C. Induction Permeability d. 14. A capacitor will experienced internal overheating. This is due to which of the following? a.. Leakage resistance b. Electron movement C. Dielectric charge d. Plate vibration 15. What is the property of a capacitor to store electricity? a. Retentivity b. Capacitance C. Electric intensity Permittivity 8. 9. C. d. III. Problem Solving 1. Two coils A and B known to have the same resistance are connected in series across a 110 - V, 60 Hz line. The current and power delivered by the source are respectively 12.3 A and 900 W. If the voltage across the coil A is three times that across coil B, give the ratio of the inductance of coil A to the inductance of coil B. 2. A single phase load takes 75 kW at 75% p.f. lagging from a 240 V, 60 Hz supply. If the supply is made 50 Hz, with the voltage twice, what will be the kW load at this rating? Give also the complex expression of the impedance. A non-inductive resistance of 15 ohms in series with a condenser takes 5 A from 220 - V ,60 Hz mains. What current will this circuit take from 220-V, 25 Hz supply? 3. An industrial coil has a resistance of 64 ohms and a reactance of 48 ohms and rated 440 V at 60 Hz. A factory will connect the coil to a 440 V, 50 Hz supply. How much percentage over current will the coil suffer? 5. A coil (RL) is connected in series with a capacitor across a 220 V, 60 Hz AC supply. The circuit is designed such that the voltage across the coil is half of that capacitor. If the circuit operates at 0.80 leading power factor, determine the magnitude of the voltage across the coil and of that capacitor. 6. Show that lave = 0.63661 Answer Key 1. Ratio = 2.472 P = 346.45 kW I₂ = 2.19 A % overcurrent = 6 % EL = 254 cis 46.15 V; Ec= 127 V Derivation God bless. Prepared by: Alto MELVIN G. OBUS Instructor 2. 3. 4. 5. 6.