Analogue Electronics (EO127A)

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School of Computing, Engineering andMathematics

Division of Engineering and Product Design

Semester-OneExaminations,January 2011

B.ENG. HONOURS DEGREE & FD.ENG.

ANALOGUE ELECTRONICS (EO127A)

EXAMINER: DR. D. S. GILL

Instructions to Candidates:

The time allowed isTWO hours

AttemptALL questions

The total number of questions is FOUR

Each question carries25 marks

This is a Closed-Bookexamination

All workings should be shown.

Special Requirements:

None

Question 1

Study the following circuit carefully:

Fig Q1

(a)Determine the values of the components for the Thévenin equivalent circuit for the circuit of FigQ1 (without RL). Your answer will include full annotated diagrams.

(10 marks)

(b)Determine the Norton equivalent circuitfor the circuit of Fig Q1 (without RL). You may use the results from part (a) to arrive at your answer.

(7 marks)

(c)Calculate the value of the current flowing out of terminal A and the voltage across the terminals A & B when RL is attached to the network as shown in FigQ1.

(8 marks)

Question 2

Study the following circuit carefully:

Fig Q2

(a)Determine the current flowing through resistor R1 in FigQ2 above using Mesh Analysis.

(13 marks)

(b)Verify your answer using Nodal Analysis.

(12 marks)

Marks will be given for your working in both cases.

Question 3

Fig Q3

(a)Determine the peak value of the applied voltage source.

(3 marks)

(b)Calculate the effective impedance of the circuit; i.e. the combined impedance of the resistor, inductor and capacitor.

(10 marks)

(c)Determine the magnitude and phase of the voltage across the capacitor, and the magnitude and phase of the current flowing in theinductor, showing all working.

(12 marks)

Question 4

(a)An AC voltage source can be represented by the following equation:

V = 10 sin(100t)

Determine the RMS value of the voltage source as well as the signal frequency in Hz, giving reasons for your answer.

(4 marks)

(b)This voltage source is fed to a load comprising of a resistor of 10kΩ in series with a capacitor of 10µF.

Calculate the total impedance of the load, showing all working.

(6 marks)

(c)Determine the voltages across each component (i.e. the voltage across the resistor and the voltage across the capacitor), expressing your answer in polar coordinates. Marks will be given for your working.

(7 marks)

(d)The frequency of the applied voltage source to the circuit of part (b) is now changed to 100kHz.

Sketch the waveform of one cycle of the new applied voltage, taking care to indicate the period of the waveform as well as the peak voltage.

Determine the total impedance of the load. Comment on the effect the change of frequency has on the impedance of the capacitor.

(8 marks)

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