FEE 2020 PDF - Fundamentals Electrical Engineering Exam

MUSTER Prüfungsbogen: 0 evaexam FHWS Prof. Dr.-Ing. Jan Hansmann FE Fundamentals Electrical Engineering Bitte so markieren:...

MUSTER Prüfungsbogen: 0 evaexam FHWS Prof. Dr.-Ing. Jan Hansmann FE Fundamentals Electrical Engineering Bitte so markieren: Bitte verwenden Sie einen Kugelschreiber oder nicht zu starken Filzstift. Dieser Fragebogen wird maschinell erfasst. Korrektur: Bitte beachten Sie im Interesse einer optimalen Datenerfassung die links gegebenen Hinweise beim Ausfüllen. Bitte ausfüllen (Die Angabe des Namens ist freiwillig.): Prüfungsteilnehmer-ID für den Prüfungsbogen Nr.: 0: Vorname: 1 2 3 4 Nachname: 5 6 7 Für die eindeutige Zuordnung der Prüfung übertragen Sie bitte 8 Ihre Prüfungsteilnehmer-ID gewissenhaft in die dafür 9 vorgesehenen Felder. Alle Seiten sind vollständig individualisiert und nicht mit anderen Prüfungen tauschbar. 0 1. Direct Current - Sources, Loads and Circuits You are given a real voltage source. Without a load, the voltage at the output terminals is U0 = 12 V. When a load is connected, a current of I of 15 A is measured. The voltage over the load is reduced to UL = 11.5 V. 1.1 A real voltage source consists of an ideal current source and a resistor in parallel. a ideal current source and a resistor in series. an ideal voltage source and a resistor in parallel. an ideal voltage source and a resistor in series. 1.2 According to the information provided above, the source voltage in a respective equivalent circuit for the real voltage source equals 11.5 V 12 V 12.5 V F19576U0P1PL0V0 24.01.2022, Seite 1/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 1. Direct Current - Sources, Loads and Circuits [Fortsetzung] 1.3 According to the information provided above, the resistance of the internal resistor in a respective equivalent circuit for the real voltage source equals 0.033 Ohm 0.0331 Ohm 0.0333 Ohm 0.0334 Ohm 0.0336 Ohm F19576U0P2PL0V0 24.01.2022, Seite 2/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 2. Direct current - Circuit analysis You are given the following circuit. Hereby, the source voltage US equals 48 V. The resistors have the following values, R1 = 100 Ohm, R2 = 100 Ohm, R3 = 50 Ohm and R4 = 100 Ohm. 2.1 Which of the following statements is correct. R1 is in parallel to R2. R2 is in parallel to R3. R2 is in parallel to R4. 2.2 The current I1 equals 0.24 A 0.48 A 0.72 A 2.3 The current I3 equals 0.24 A 0.48 A 0.72 A 2.4 The current I4 equals 0.24 A 0.48 A 0.72 A 2.5 The current I equals 0.24 A 0.48 A 0.72 A F19576U0P3PL0V0 24.01.2022, Seite 3/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 3. Node voltage analysis You are given the following DC circuit. 3.1 a) How many essential nodes does the circuit have? 1 2 3 4 3.2 a) How many redundant resistors are in the circuit? 1 2 3 4 3.3 Problematic is the voltage source as the current IS through the voltage source is unknown. To overcome this issue, which of the following methods is or are applicable? Source conversion. Introduction of a super node. Maximum power transfer theorem. Introduction of a phasor diagram. F19576U0P4PL0V0 24.01.2022, Seite 4/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 3. Node voltage analysis [Fortsetzung] We continue using source conversion. Then, the circuit looks as followed. 3.4 Please perform Kirchhoff current law (KCL) at node A. 3.5 Please perform Kirchhoff current law (KCL) at node B. 3.6 The current IS equals 0.2 A 0.4 A 0.6 A 0.8 A 1.0 A 3.7 The voltage of node A equals. V F19576U0P5PL0V0 24.01.2022, Seite 5/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 3. Node voltage analysis [Fortsetzung] 3.8 The voltage of node B equals. V F19576U0P6PL0V0 24.01.2022, Seite 6/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 4. Superposition You are given the following circuit. To find the voltage between the nodes A and B, superposition is used. 4.1 To perfom superposition, how many times do you need to redraw the circuit and find a partial voltage? 1 2 3 4 4.2 Following finding all partial voltages, the next step is to multiply all partial voltages. average all partial voltages. add all partial voltages algebraically. 4.3 Please select the correct statement(s). Superposition can be used for linear and nonlinear networks. Superposition can only be used for nonlinear networks. Superposition can only be used for linear networks. 4.4 Please select the correct statement(s). For superposition, voltage sources are replaced with shorts, and current sources are replaced with open circuits. voltage sources are replaced with open circuits, and current sources are replaced with shorts. only voltage sources are replaced. only current sources are replaced. 4.5 We start with the voltage source US1 and calculate UAB,US1. When calcuating the partial voltage induced by this source we find UAB,US1 as UAB,US1 = R1/(R1+R2+R5) * US1 UAB,US1 = (R4+R5)/(R1+R4+R5) * US1 UAB,US1 = R1/(R1+R2+R3) * US1 UAB,US1 = 1/2 * US1 F19576U0P7PL0V0 24.01.2022, Seite 7/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 5. Alternating currents - signal analysis At an impedance Z, the following signals for the alternating current i(t) and the alternating voltage u(t), are measured with an oscilloscope. The current is presented as solid line and the voltage is depicted as dashed line. For the x-axis, the resolution is 10 ms per division. For the y-axis, one division equals to 1 V or 100 mA. 5.1 Please derive the frequency f for the signals measured with the oscilloscope. f = 2.5 Hz f = 25 Hz f = 250 Hz 5.2 The amplitude of the current is 100 mV 200 mA 300 mA 5.3 The amplitude of the voltage u(t) is 1V 200 mA 4V 5.4 Which of the following statements is or are correct? Current and voltage are in phase. Current lags the voltage by 180 °. Current lags the voltage by 90 °. Voltage lags the current by 180 °. Voltage lags the current by 90 °. Voltage leads current by 90 °. F19576U0P8PL0V0 24.01.2022, Seite 8/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 5. Alternating currents - signal analysis [Fortsetzung] 5.5 Which of the following phasor diagrams is or are correct (only qualitatively and not the length of the phasors)? (a) (b) (c) (d) 5.6 What is a suitable circuit for the unknown impedance Z? (a) (b) (c) (d) F19576U0P9PL0V0 24.01.2022, Seite 9/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 6. RLC-circuits You are given the following AC circuit. The frequency of the alternating sinusoidal voltage source is 1 kHz and the RMS value of the voltage is 10 V. The resistor has R = 100 Ohm, the inductor L = 10 mH, and the capacitor C = 1 µF. 6.1 The real part of the total impedance of the circuit is (Please use 1234 Ohm instead of 1.234 kOhm). Ohm 6.2 The capacitive reactance of the circuit is (Please use 1234 Ohm instead of 1.234 kOhm). Ohm F19576U0P10PL0V0 24.01.2022, Seite 10/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 6. RLC-circuits [Fortsetzung] 6.3 The inductive reactance of the circuit is (Please use 1234 Ohm instead of 1.234 kOhm). Ohm 6.4 The magnitude of the total impedance of the circuit is (Please use 1234 Ohm instead of 1.234 kOhm). Ohm 6.5 Which of the following statements is or are correct? Current and voltage are in phase. Voltage leads current. Current leads voltage. The circuit is apparent inductive. The circuit is apparent capacitive. F19576U0P11PL0V0 24.01.2022, Seite 11/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 7. Filter You are given the following frequency-dependent circuit. The circuit comprises two inductors with L1 = 15 mH. For a frequency f1 = 3.5 kHz, the magnitude of the transfer function should be 1. For a frequency f2 = 2.5 kHz, the magnitude of the transfer function should be 0. Please find C and L2. 7.1 Please find C. Therefore, please explain briefly your approach in the text box. C= nF F19576U0P12PL0V0 24.01.2022, Seite 12/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 7. Filter [Fortsetzung] 7.2 Please find L2. Therefore, please explain briefly your approach in the text box. L2 =. mH F19576U0P13PL0V0 24.01.2022, Seite 13/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 8. Balanced three-phase circuits You are given the following balanced three-phase circuit. 8.1 In the balanced three-phase circuit, the current in the neutral line is 0A 1A 0A F19576U0P14PL0V0 24.01.2022, Seite 14/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 8. Balanced three-phase circuits [Fortsetzung] The impedances in the Lines L1, L2, and L3 result in the currents as shown in the following figure. 8.2 The current in the neutral line N equals -4A+j1A 4A+j2A 2A-j4A 4A+j4A F19576U0P15PL0V0 24.01.2022, Seite 15/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 9. General question - let's go and get some points 9.1 The complex conjugate of -a+jb (j is the imaginary unit) is a-jb -a-jb -a+jb 9.2 If four equal resistors are connected in parallel, the total resistance is one fourth of the resistance of an individual resistor. four times the resistance of an individual resistor. 16-fold the resistance of an individual resistor. 9.3 The capacitance of a capacitor can be decreased by increasing the distance between the plates. increasing the area of the plate. decreasing the distance between the plates. 9.4 At a capacitor in an alternating current circuit, no true power is dissipated. only true power is dissipated. Square root of 2-times the product of current and voltage is dissipated. 9.5 A capacitor with a capacitance of 1 µF is connected in parallel to a capacitor with 2 µF. The total capacitance is > 2 µF < 2 µF < 1 µF 9.6 An inductor of 1 mH in parallel with an inductor of 2 mH results in a total inductance of 1.5 mH < 1.0 mH > 2 mH 9.7 The time constant of a series circuit composed of an inductor (2 mH) and a resistor (1 kOhm) is 0.5 µs 0.5 s 2s 2 µs 9.8 To compensate the reactive power at a load, a resistor should be connected in parallel to the source. an impedance should be added in parallel the load. a resistor should be added in series to the load. 9.9 In a Bode plot, the slope of transfer function of a RC low pass filter with order of 1 for frequencies higher than the cut- off frequency is -20 dB/decade -20 dB 1 dB/decade +20 dB 9.10 A unit of power is Joule kilowatt-hour both previous options are correct none is correct F19576U0P16PL0V0 24.01.2022, Seite 16/17 MUSTER  MUSTER Prüfungsbogen: 0 evaexam 9. General question - let's go and get some points [Fortsetzung] 9.11 If the voltage at a resistor is doubled, the dissipated power is halved unchanged doubled quadrupled 9.12 The impedance of a resistor is always real. always imaginary. composed of real and imaginary parts. 9.13 The impedance of an inductor and a capacitor are calculated using only on frequency. only on component parameters. frequency and component parameters. 9.14 Superposition can not be used for circuits with more than two sources. nonlinear circuit. circuits with current sources. circuits with real sources. 9.15 A resistor is linear nonlinear 9.16 To solve a set of linear equations, the number of independent equations is at least 1 2 3 4 equal to the number of unknowns. 9.17 When connected via a resistor to a constant voltage source, a capacitor will reach 50 % of final the voltage in less than one time constant. exactly one time constant. later than one time constant. the answer depends on the voltage. 9.18 When a sinusoidal voltage is applied to a capacitor, the current will lag voltage by 90°. lag the voltage by 45°. be in phase with the voltage. lead the voltage by 90°. 9.19 When a capacitor is connected to a constant voltage source via a resistor, the current at the capacitor over time is linear curve. a rising exponential curve. a decaying exponential curve. none of the options above. F19576U0P17PL0V0 24.01.2022, Seite 17/17 MUSTER