Los marcos discursivos decimonónicos y el agua

3.3.1 Methodology and Context

Carefully designed laboratory activities are required for the effective use of the VEL. They can make invaluable contributions to students’ learning [26]. The onus is on the instructor to design laboratory activities that promote students’ understanding of concepts and to ensure that each practical exercise fits in with the overall aims of its focus course unit. Ideas and practical guides for this have been given by [2].

For instance, the instructor can methodically group the contents of a course unit into knowledge goals. Each knowledge goal can have a set of outcome and pre-requisite concepts. The latter are the concepts learners should have prior knowledge of, as “stepping stones” for learning the outcome concepts. The instructor can design concept-based laboratory activities and group them into sessions. Each laboratory session can address a specific knowledge goal while one or more laboratory activities in a session can address aspects of an outcome

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concept, with clear learning objectives. Learning objectives are essential in applying an effective system of assessment [10]. This approach ensures that students carry out concept- based laboratory activities aimed at enhancing their understanding of the concept. An example of a knowledge goal is Filters whose outcome concepts include notch, low-, high-, and band- pass passive RC filters, at the fundamental level (see Table 3.2).

Table 3.2: A knowledge goal and its outcome and pre-requisite concepts

S/No.

Knowledge Goal: Passive RC Filters

Outcome Concept Pre-requisite

1 Low pass filter

R, L, C circuit components characteristics.

RC, RL, RCL circuits

2 High pass filter

3 Band pass filter

4 All pass filter

5 Band reject (Notch) filter

S/No.

Knowledge Goal: Passive RC Filters

Outcome Concept Pre-requisite

1 Low pass filter

R, L, C circuit components characteristics.

RC, RL, RCL circuits

2 High pass filter

3 Band pass filter

4 All pass filter

5 Band reject (Notch) filter

Along these lines, a set of laboratory activities aimed at enhancing students’ understanding of passive RC filters were designed, to be undertaken by students in the VEL environment. The activities were designed around two related course units in two different engineering faculties at two separate Universities:

1. a 2nd year unit on Analogue Electronics and Circuits at the ECE department of University of Portsmouth (UoP). An aspect of the unit involves the design, building and analysis of passive RC filter circuits.

2. a 3rd year unit on Engineering Studio and Network Theory, at the EEE department of UTON, which addresses passive RC filters as part of its contents.

This was to facilitate the evaluation of the VEL at both Universities, using the same set of laboratory activities, Pre-Test and Post-Test (PTPT) and feedback form, albeit at different time periods.

3.3.2

Sample Student Cohorts

At UoP, only 30% of the class that took the analogue electronics and circuits unit volunteered and participated in the evaluation exercise (NP = 9). At UTON, most of the students that took

the course unit on engineering studio and network theory were willing and eager to participate in the evaluation exercise, but participation was limited to only 13% of the students (NF = 52)

basis. The UoP and UTON student cohorts make up the total sample (N = 62). The gender distribution of the student cohorts were: 11% female (n = 1) and 89% (n = 8) male in the UoP cohort; and 10% (n = 5) female and 90% (n = 47) male in the UTON cohort. The samples did not include physics students and students from other fields of engineering who took the units as electives or compulsory units. All were undergraduate EEE (at UTON) and ECE (at UoP) students.

3.3.3

Evaluation Process

The aim of the evaluation process was to verify the effectiveness of the VEL as a tool for enhancing students’ understanding of fundamental engineering concepts taught in lectures. PTPT observation technique was used to generate data for statistical analysis. PTPT is a widely used evaluation/assessment technique and is accepted as a reliable means of assessing learning and changes in knowledge [134][135]. Its use cuts across numerous disciplines. PTPT assessment is objective and offers a valuable set of data for evidencing increased knowledge with respect to specific concepts [135].

The PTPT consisted of Multiple Choice Items (MCIs). The items had the correct answer and three distracters for answer choices. The distracters were equally plausible, but incorrect and students were not timed for their responses to the items. The items were instruments designed as part of this work, in consultation with domain experts, course syllabi, proposed goals and course objectives. Despite the contested suggested limitations of MCIs, they are being increasingly used in higher education, as a result of growing student numbers, reduced resources and increasing use of new technologies [136]. Moreover, MCIs afford opportunities for rapid feedback and savings in marking time. Also, there was need to take advantage of the fact that the feedback provided by MCIs can be predetermined during test construction. [17], in addition to many other researchers, used the MCI-based PTPT technique for evaluating students’ learning before and after an educational intervention.

Both student cohorts had taken lectures on passive RC filters, having learnt the pre-requisite concepts earlier. A pre-test was used to evaluate the students’ knowledge of the addressed concept(s) before undertaking the laboratory activities in the VEL environment. Pre-testing was done after the addressed concepts had been taught in lectures, but before the students were exposed to the VEL environment. After taking the pre-test, the students then went ahead to undertake a set of laboratory activities in the VEL environment. The laboratory activities were designed to address four types of passive RC filter concepts: low-pass, high-pass, band-

pass, and notch. The PTPT were constructed to elicit students’ knowledge of these filter concepts. The students undertook the laboratory activities at their own pace. The researcher and other persons were available to offer students necessary support. In addition, the students were provided tips and procedure on the usage of the VEL.

The students were aware that their work processes were being unobtrusively “observed” and logged. As sample screenshots, Figure 3.6 shows one of the laboratory activities undertaken by students and Figures 3.7 and 3.8 show a student’s built circuit and graphical output, respectively, while undertaking the laboratory activity of Figure 3.6 in the VEL environment. The graphical output of Figure 3.8 was produced for the frequency range of 1000 (start frequency) to 10000 (end frequency), at 50 points per decade. On completion of the laboratory activities, in addition to taking a post-test, the students anonymously completed a usability feedback instrument.

The post-test was used to assess the impact of undertaking the laboratory activities in the VEL environment, on the students’ learning of the addressed concept(s). The aim was not only to assess whether the educational intervention had had, possibly, a positive impact on the students’ understanding of the addressed concepts, but also, to be able to quantify the impact. The post-test was administered immediately, on completion of the laboratory activities. The post-test items contained nearly twice as many items as the pre-test. All the items in the pre- test were included in the post-test, in addition to other items that assessed the same expected learning outcomes.

ACTIVITY-504: Passive RC Filters: Notch filter.

AIM: To study the filtering characteristics of Notch RC filter

Design a twin-T passive notch filter (RC only) capable of rejecting frequencies in the 3KHz to 3.5KHz frequency band (see the figure below). Assume C = 1µF. 1. Build the filter you have designed on a breadboard. Using a sinusoidal signal source of 1Vrms value, generate the frequency response curve for the circuit (without loading the circuit).

2. Load the circuit you have built with a 1 KΩ resistor and generate the frequency response curve of the loaded circuit.

a.) Use a single word to describe the shape of the curve generated. b.) Is the frequency response of the filter affected by the load? c.) If the answer to question b.) is yes, state how.

3. Reading the curve of the frequency response, what is the maximum rejection frequency?

Passive RC notch filter ACTIVITY-504: Passive RC Filters: Notch filter.

AIM: To study the filtering characteristics of Notch RC filter

Design a twin-T passive notch filter (RC only) capable of rejecting frequencies in the 3KHz to 3.5KHz frequency band (see the figure below). Assume C = 1µF. 1. Build the filter you have designed on a breadboard. Using a sinusoidal signal source of 1Vrms value, generate the frequency response curve for the circuit (without loading the circuit).

2. Load the circuit you have built with a 1 KΩ resistor and generate the frequency response curve of the loaded circuit.

a.) Use a single word to describe the shape of the curve generated. b.) Is the frequency response of the filter affected by the load? c.) If the answer to question b.) is yes, state how.

3. Reading the curve of the frequency response, what is the maximum rejection frequency?

Passive RC notch filter

Figure 3.6: One of the laboratory activities undertaken by students in the VEL environment

Figure 3.7: A student’s built circuit for the laboratory activity of Figure 3.6, in the VEL environment

Figure 3.8: A student’s graphical output for the laboratory activity of Figure 3.6