Hybrid Courses Based on Basic Sciences and Green Technologies in Engineering Programs ^†

Abstract

An ineluctable topic has emerged and needs to be treated in engineering programs for green energies. Particularly in the programs of electrical and systems engineering, students can acquire the capabilities to envision the arrival of green standards to generate clean energy sources. In this article, the introduction of new forms of green energy is systematically presented through a basic experiment in electricity in which a potato is used to investigate the current and electric power. The experiences were conducted at the 2022-I at a private university in Lima City. The results demonstrated that the topic of biofuel in the framework of green energy can be studied in undergraduate courses. Indeed, prospective students of engineering can be oriented toward research in engineering for the implementation of new electrical systems that provide electricity with low budgets.

1. Introduction

An appropriate time to show the promising green technologies to freshmen [1,2,3] would be the first semester. In particular, all programs in engineering have to be aggregated in the curricula. Important topics would be the following.

• Searching for green batteries
• Green energy for massive applications
• Software to manage green energies
• Use of ongoing technologies in the green scenario

Thus, the potential ways to teach these topics and the abilities of freshman students to think about them in the future are necessary. With the massive usage of smartphones, tablets, and laptops, the main question about the topic is what green technologies are used to replace conventional batteries [4,5].

The topics about green technologies can be relevant to various factors such as motivation, perspective, compromise in chosen programs, and research aspects. Thus, attention has been paid to the basic courses of physics [6,7], in which a simple scheme is presented for students to gain knowledge to create new circuits based on biological waste. From the well-known experiment to understand electric fields and Ohm’s law, the implementation of biological compounds as a replacement for electrical circuits is presented.

The potential usage of waste as a source of energy is examined as a course of physics-II in the system engineering department iofn a private university located in the south pole of Lima City.

The course teaches the following topics.

• The theory of equipotential lines
• The experience of lines of electric fields
• The usage of wasted potatoes
• The demonstration of Ohm law
• Presentation of scenarios in which the waste replaces electrical batteries.

In the experience, students are required to have a solid background in math, particularly calculus, as Gauss law and vectorial analysis are demanded for a solid understanding of the experiment. This encompasses the idea that, in conjunction with theory, math and experiments must be learned together [8,9,10]. This is the foundation on which students embark to learn new green technology. Thus, the purpose of this study is to present the design of the course in which the topics of physics are taught and to provide capabilities to face the new technologies through basic sessions of experiments.

The paper is structured as follows. In the second section, the content of the session based on theory and experiment is described. In the third section, Ohm’s law and a bio-circuit are explained using the peels of potatoes as a source of electric energy. Finally, the conclusion is drawn.

2. Session of Physics

In this section, the design of a session of physics (level 2) in the program of system engineering is presented. According to the content of the course, the topic corresponds to a concrete experience in the verification of equipotential lines. The theory is established on the concepts of vectors and Coulomb’s law [11,12,13].

Students need to understand the sequence of equations.

$$\frac{\mathit{F}}{q}=\mathit{E}=\int d\mathit{E}=\int \frac{dQ(\mathit{r}-{\mathit{r}}^{\prime })}{{\left|\mathit{r}-{\mathit{r}}^{\prime }\right|}^3}$$

(1)

where 4 π ε_0 = 1. With the definition of Coulomb’s law, the electric fields can be derived. Through a mathematical procedure based on vectorial calculus, (1) is derived.

$$\mathit{E}=-\nabla \left[\frac{Q}{\left|\mathit{r}-{\mathit{r}}^{\prime }\right|}\right]$$

(2)

Students can recognize the term in brackets which constitutes the electric potential Φ, and has a direct relation with the Coulomb force, which is given by:

$$\mathit{F}=\mathit{q}\mathit{E}=-\nabla \left[\frac{qQ}{\left|\mathit{r}-{\mathit{r}}^{\prime }\right|}\right].$$

(3)

Direct communication with students specifies the necessity to implement the gradient operator “∇” in (2). It is expected that students pass up to the second course of calculus in which the gradient operator is linked to a geometrical view such as the tangent. Students are asked to simulate the system of two electrodes with opposite signs. Here, the use of an external package in the session combines the usage of math at the basic level [14,15,16]. In this way, the session employs Wolfram, which allows students to simulate two electrodes emitting lines of electric fields.

Figure 1 shows the 3D representation of three spatial variables. Students use the Gaussian functions and their product to the second-order polynomial. Two well-defined Gaussian functions are separated at a distance between the electrodes. Although it is not a direct mathematical manifestation of two electrodes, the use of mathematical packages allows the simulation of the spatial position of real electrodes.

Once the simulation of electrodes is completed, the next step is the use of Wolfram to reconstruct the lines of the electric field as well as the equipotential lines. The use of directives in physics with Wolfram is to determine the possible topology of lines. Thus, the command is conducted by students (Figure 2).

According to Figure 1 and Figure 2, students can complement the assimilated theory to define the experimental arrangement through in-situ verification. Figure 3 shows the basic arrangement. A bucket, two electrodes, a voltmeter, and a power source to provide 10 V are required in the experiment to understand the field and equipotential lines. It is important to note that the instructor can modify the geometry of electrodes, such as circular, rectangle, and others. Thus, the emission of field lines shows the dependency of the geometry of the source.

While using Wolfram for a theoretical simulation of involved physics, students witness the physics of Coulomb’s law and the gradient operator, which constitutes an educational objective in the program.

3. Usage of Potato Peels

In South America, the consumption of potatoes is general, so there are lots of peels. Thus, the idea is to reuse the peel as biological materials for producing electricity [18,19,20]. Therefore, the peel in the experiment of equipotential lines is used to measure the main electrical parameters and test the potential capability in a real circuit. From (3), the electric field is defined as

$$\mathit{d}\mathit{E}=\frac{dQ}{{\left|R\right|}^2}.$$

(4)

From ρ = dQ/dV,

$$\mathit{d}\mathit{E}=\frac{\rho dV}{{\left|R\right|}^2}.$$

(5)

By keeping a spherical symmetry,

$$\frac{1}{4\pi }\mathit{d}\mathit{E}=\frac{\rho (R,\alpha ){dRR}^2}{{\left|R\right|}^2}.$$

(6)

Then, the electric field can be written as:

$$\mathit{E}=\frac{1}{4\pi }\int \mathit{d}\mathit{E}=\int \frac{\rho (R,\alpha )R^{2}dR}{{\left|R\right|}^2}.$$

(7)

$\rho (R,\alpha )$ is a volumetric charge density depending on the radius, and α is a parameter characterizing the density of electric charge.

The measurement of electricity before and after adding the peel to water is performed to see if the peel is forming an electric field and is changing the electrical configuration.

Figure 4 shows that in presence of a charged compound, the lines of the field are distorted, this suggests the deformation of equipotential lines [21]. Thus, such a phenomenon triggers the deformation of equipotential lines with the peel of potatoes. Figure 5 shows the experiment with 150 g of the peel. The peel is introduced in 0.3 L of water. With a power source of 10 V, the equipotential lines are dramatically changed yielding 5.54 and 4.96 V. The electric field is affected as

$$\mathit{E}=\lambda \mathcal{l}+\int \frac{\rho (R,\alpha )R^{2}dR}{{\left|R\right|}^2}$$

(8)

where “λ” is the linear charge density and l is the length of the metallic bar in the bucket. A mathematical form for $\rho (R,\alpha )$ is a nonlinear function. Electric charges can be found in the proteins of potatoes. This is the reason why the deformation of field lines is presented in Figure 4. The arrow indicates the place of the peel of the potato emitting asymmetric field lines without following any pattern. From the above, students understand that the peel of the potato exhibits electrical properties.

4. Ohm Law and Proposal for Green Energy Circuit

Once the peel of the potato is recognized by students as an inherent bio-electrical component, in the next session, the introduction of circuit laws such as Ohm’s law is explained. Students are encouraged to pay attention to the theoretical and experimental points of Ohm’s law. For this, the difference in electrical potential is discussed (see Figure 5), and resistance is introduced. The tool turns out to be useful for observing Ohm’s law [22]. Figure 6 shows two resistors, R₂ and R₃, in parallel and in series to R₁. Theoretically, Ohm’s law is expressed as

$$V=\frac{R_2{R}_3}{R_2+R_3}I,$$

(9)

While factorizing “R_2”,

$$V=\frac{R_2{R}_3}{R_2\left(1+\frac{R_3}{R_2}\right)}I=\frac{R_3}{\left(1+\frac{R_3}{R_2}\right)}I.$$

(10)

The denominator has the below form if ${\left(\frac{R_3}{R_2}\right)}^q\approx 0$ for $q\ge 2$ then

$$Exp\left(\frac{R_3}{R_2}\right)\approx 1+\left(\frac{R_3}{R_2}\right){+\frac{1}{2!}\left(\frac{R_3}{R_2}\right)}^2{+\frac{1}{3!}\left(\frac{R_3}{R_2}\right)}^3+\cdots$$

(11)

Therefore, (10) is written as

$$V=Exp\left(-\frac{R_3}{R_2}\right)I{R}_3.$$

(12)

Equation (12) behaves like a Weibull distribution from the fact that these probability distribution functions can be written as $f\left(x\right)=x^{k+1}{e}^{-x^k}$. Thus, the replacement of “$R_3$” by peel potato is interesting for students who verify that biological compounds can serve as biodevices. The peel of the potato can also be an “extra” power source in water, as shown in Figure 6.

In Figure 7 the equivalent electrical circuits done with PASCO is displayed. When “$R_3$” becomes a power source, an advanced theory of circuits is applied. The instructor suggests demonstrating the theorem of Thevenin and experimenting. When “$R_3$” is a power source, the Thevenin voltage and current are determined, then “$R_2$” is removed. Thus, when “$R_3$” = $V_B$ the biological power source is applied with Kirchhoff’s law as follows:

$$I=\frac{R_2+R_3}{R_2{R}_3}{(V}_B-V).$$

(13)

The student can check out the linearity between the Thevenin’s current and the difference in voltage “$V_B-V$”. Any difference between the current from (13) and the derived equation from (11) is written as:

$$I=\frac{V}{R_3}Exp\left(\frac{R_3}{R_2}\right),$$

(14)

Mass and humidity are relevant parameters. When “R_3” is replaced by the peel of the potato, a current is obtained depending on the potato-like resistor exhibiting a two-zone behavior when I(R_3) is plotted. Thus, the student can try other forms with the waste of fruits, spoiled food, or another biological compound for searching new green technologies. Finally, in

Table 1. Outcomes of Experience.

Variable	Impact	In Campus	Outside Campus
Communication	Middle	Yes	Yes
Workshop	Middle	Yes	No
Review of literature	High	Yes	Probable
Sociability	High	High	High

, the outcomes of the whole experience are listed. It is noteworthy that variables have shown to keep a direct relationship to student satisfaction, being this very import to avoid desertion. Thus, communications among students were optimal, task and workshop were done in home. However, it is not clear if students after lab have had the chance to improve the gained knowledge. In addition, the lab is clearly a healthy space to demonstrate sociability among students. Future work, shall be analyzed the issue of impact of physics laboratory onto the formation of engineers, as well as the period after the finishing the grade of bachelor of engineering.

5. Conclusions

In this study, experiences on the use of the peel of the potato as a potential candidate for a green device in electrical circuits are obtained with the theoretical foundation about the role of the biological resistor. This can be introduced in the second course of physics to motivate students to understand the construction of electrical circuits with the prospective use of biomaterials [23,24,25].