UPD EEE 118 Practical Exam 1 (2025-2026 First Semester)

The following page is based on the EEE 118 practical exam taken in the first semester of academic year 2025-2026. 

General Instructions

1. Read instructions carefully. Deductions will be given by not following instructions. 
2. You're given 12 minutes per station. After this time, you'll be given at most 2 minutes to clean up and re-set the station. 
3. Important: After each station, reset the station completely. Return all wires to their original positions. Remove any additional components added to the breadboard, if any. Leave all equipment powered on. Manually restore settings to their original configuration before you leave the station. 
4. There are five (5) stations. The exam has a total of 100 marks. 
5. You may only work on the questions for the station where you are assigned. You're not allowed to go back to a previous section or skip ahead. 
6. Observe total silence while taking the practical exam. 
7. Show your solutions on the space provided. Please write legibly. Use black or blue ink only. 
8. Use four significant figures unless otherwise stated. 

Good luck!

Station 1: Draw the Circuit - Breadboard to Schematic Diagram

The assembled circuit below lights up an LED. Before starting, ensure that your power supply is on. 

Task: Complete the schematic diagram. Clearly label all components, values, and polarities. A clean, standard schematic is preferred. No erasures! (25)

Important: Don't move or reposition any component. The push button is fixed in place. You may press it, but its position in your schematic layout must remain unchanged. Don't turn off the power supply when you leave the station. 

Bonus: What does the capacitor do in this circuit? (1)

Station 2: Using the Digital Multimeter for DC Measurements

You're provided with a resistor network powered by a 5V DC supply. Use a digital multimeter to perform the following measurements. Record the full value displayed on the DWM, including all decimal places. Don't round off and don't forget to include the units.

1. Ensure that the circuit is powered up. Using the DMM as a voltmeter, measure the following voltages: (3 marks each)
   • V1: Voltage across the 10 kOhm resistor
   • V2: Voltage across the left parallel 10 kOhm resistor
   • V3: Voltage across the right parallel 10 kOhm resistor

   Bonus: Do we expect any of the three voltages to be equal? Explain. (0.5)

2. Using the DMM as an ammeter, measure the following currents. You are free to tinker with the circuit and use additioanl wires to properly measure the currents. Ensure that the circuit is powered on when taking circuit measurements. The ammeter must be connected in series with the component being measured. (4 marks each)
   • I1: Current through the series 10 kOhm resistor
   • I2: Current through the left parallel 10 kOhm resistor
   • I3: Current through the right parallel 10 kOhm resistor

   Bonus: Explain how I1 compares to I2 and I3 (0.5)

3. Disconnect the power supply. Using the DMM as an ohmmeter, measure the equivalent resistance seen from the source terminals. (4)

Important: Be sure to reconnect the power supply after doing this item. Reset the station completely for the next user.

Station 3: Exploring AC Signal Behaviour

Implement the circuit shown below. Using the signal generator, set Vin as a sine wave with a peak-to-peak voltage of 6 V, no DC offset, and a frequency of 1 kHz. Set R = 5.1 kOhm and C = 0.01e-6 F. Ensure that your plots are neat and labeled clearly, and don't forget to include appropriate units in your answers.

1. Plot the superimposed input and output waveforms on the gird. Label the voltage and time axes with appropriate tick marks. Draw at least two full cycles, and clearly indicate the extremum voltages, the period of one cycle, and which waveform corresponds to Vin and Vout. Incomplete or missing labels may be penalised. (15)
2. Measure the time difference. Use the oscilloscope's cursor feature and measure between similar points on the waveforms. (10)

Bonus: In this circuit, suppose the signal generator suddenly outputs a constant DC voltage instead of a sine wave. After some time, how will the capacitor behave in this circuit? (0.5)

Station 4: Observing the Behaviour of an Operational Amplifier

The circuit, as demonstrated below, implements a basic operational amplifier configuration with resistor values Ri = 1 kOhm and Rf = 10 kOhm. The operational amplifier used is the LM741, powered by 12 V. The input signal is a sine wave with a minimum voltage of -500 mV, a maximum voltage of 500 mV, no DC offset, and a frequency of 1 kHz.

1. Plot the superimposed input and output waveforms. Label the voltage and time axes with appropriate tick marks. Draw at least two full cycles, and clearly indicate the maximum and minimum voltages, the period of one cycle, and which corresponds to Vin and Vout. Incomplete or missing labels may be penalised. (15)

   Bonus

   Identify the phase difference between the two waveforms. (0.5)

2. Replace the Rf = 10 kOhm resistor with a 33 kOhm resistor. Observe the output waveform and compare it against hte original. Describe any differences and explain this behaviour.

Bonus Station

1. Identify the equipment used so far and describe their function. (4)
2. Illustrate the proper powering-up of an operational amplifier. (1)

Markscheme

We have attached below a possible schematic that suits Station 1. For all other stations, we recommend simulating them via a SPICE program, such as LTSpice.

Station 1