This article highlights the importance of complementing classes through educational videos, especially in disciplines exclusively with lectures. This proposition is exemplified through basic concepts in alternating current for both single-phase and three-phase circuits, which are critical in the formation of electrical engineers, mechanics, chemists, etc. The main objective of conducting educational videos is to make learning more attractive and stimulate interest in acquiring the knowledge of certain topics, given their importance in professional life in different engineering areas. The videos, filmed in laboratory and of short duration, aim to complement and consolidate the content taught in the classroom lectures491491

Barreto, Gilmar

Murari, Carlos Alberto Favarin

Journal of Mechanics Engineering and Automation

English

Repositorio da Producao Cientifica e Intelectual da Unicamp

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REPOSITÓRIO DA PRODUÇÃO CIENTIFICA E INTELECTUAL DA UNICAMP
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DOI: 10.17265/2161-623X/2014.11.008
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Journal of Mechanics Engineering and Automation 4 (2014) 914-918 
 
Basic Concepts for Alternating Current through 
Educational Videos 
Gilmar Barreto1 and Carlos Alberto Favarin Murari2 
1. Department of Semiconductors, Instruments and Photonic, University of Campinas, São Paulo 13083-852, Brazil 
2. Department of Systems and Energy, University of Campinas, São Paulo 13083-852, Brazil 
 
Received: August 20, 2014 / Accepted: September 12, 2014 / Published: November 25, 2014. 
 
Abstract: This article highlights the importance of complementing classes through educational videos, especially in disciplines 
exclusively with lectures. This proposition is exemplified through basic concepts in alternating current for both single-phase and 
three-phase circuits, which are critical in the formation of electrical engineers, mechanics, chemists, etc. The main objective of 
conducting educational videos is to make learning more attractive and stimulate interest in acquiring the knowledge of certain topics, 
given their importance in professional life in different engineering areas. The videos, filmed in laboratory and of short duration, aim 
to complement and consolidate the content taught in the classroom lectures. 
 
Key words: Audiovisual, alternating current circuits, electrotechnical, engineering education, educational videos. 
 
1. Introduction 
In disciplines that basic concepts of electricity are 
addressed: single-phase and three-phase circuits; 
production, transmission and electric power use; 
physical principles and main applications of 
transformers; electrical induction machines, 
asynchronous and direct current; basics concepts of 
electrical installations and protection devices, only 
through lectures, the loss of quality in the assimilation 
of these content is inevitable. 
There are teachers who try projection of figures or 
pictures in order to facilitate understanding of the 
content and, in some cases, it has been an effective 
strategy. 
However, the ideal is to have physical space, 
equipment, teaching and technical staffs so that 
students can, by conducting appropriately designed 
experiments, verify and consolidate the theoretical 
content. 
Thus, by prioritizing the undergraduate activities 
                                                          
Corresponding author: Gilmar Barreto, Ph.D., research 
filed: automation, data modeling and engineering education. 
E-mail: gbarreto@dsif.fee.unicamp.br. 
and aware of the need for students to have a basic 
quality knowledge of alternating current circuits, the 
way we found to minimize such loss was the 
production of educational videos with experiments 
demonstration in electrotechnical. 
Thus, we have been achieving objectives such as: 
 Increase students interest in complementary and 
consolidate the content taught in lectures. The 
motivating and investigative characters cause them to 
question and seek answers in a dynamic and 
interactive manner, encouraging discussions in the 
classroom and thus increasing the student-teacher 
interaction; 
 Flexibility in access, videos as instructional 
materials (lecture notes and other texts) are available 
via the Internet. 
The production of educational videos can be helpful 
in teaching, research and extension areas, aiming to 
transmit information dynamically, enabling real 
laboratory experiments, that are not always produced 
when desire can be disseminated to all concerned. 
In Refs. [1-8], there are important comments and 
analysis on the use of educational videos and how the 
DAVID  PUBLISHING 
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Basic Concepts for Alternating Current through Educational Videos 
 
915
recordings should be made with quality and precision, 
so they are well explained without lighting and 
frameworks issues. 
The paper is organized as follows: Section 2 
contains the titles and brief descriptions of the videos 
produced to date; Section 3 describes how the videos 
were produced; Section 4 comments the receptivity of 
the videos and reproduces some of the comments 
posted by those who have watched the videos; and 
Section 5 presents our considerations on the 
importance of developing instructional video to 
disclose knowledge and motivate learning. 
2. Elaborated Educational Videos 
From scripts previously designed for carrying out 
the experimental tests, we enable the filming of the 
topics listed below, mentioning succinctly their 
contents: 
(1) Obtaining characteristic curve of dipoles (6'58"): 
voltmeter-ammeter method to obtain the characteristic 
curves of linear and nonlinear resistive dipoles; 
(2) Concept of effective value (3'53"): experimental 
realization of the concept of effective value for a 
sinusoidal waveform; 
(3) RC (resistor and capacitor) series circuit (4'02"): 
analysis of current electrical behavior against voltage 
in an RC series circuit connected to a sinusoidal 
voltage source; 
(4) RL (resistor and inductor) series circuit (4'28"): 
analysis of current electrical behavior against voltage 
in an RL series circuit connected to a sinusoidal 
voltage source; 
(5) RLC (resistor, inductor and capacitor) series 
circuit (4'27"): analysis of current electrical behavior 
against voltage in a RLC series circuit connected to a 
sinusoidal voltage source; 
(6) Three-phase load in unbalanced star (3'00"): 
importance of neutral conductor in a three-phase load 
in unbalanced star; 
(7) Three-phase voltages (3'02"): practice finding of 
the relationship between line voltage and phase in a 
three-phase electric power system; 
(8) Power factor correction (4'48"): importance of 
improving the power factor in a single-phase 
induction motor by connecting capacitors in parallel; 
(9) Electric motors (5'01"): emphasis on training of 
rotating magnetic field that guides the operation 
principle of induction and three-phase synchronous 
motors; 
(10) Determination of resistance value (5'37"): 
highlighted connections of a voltmeter and an ammeter 
in relation to a resistor to obtain the respective value; 
(11) Effective value (2'54"): determining the 
effective value of a sinusoidal wave; 
(12) Electric capacitor (2'21"): it is highlighted the 
current lag in relation to voltage, caused by a capacitor 
connected to a sinusoidal voltage source; 
(13) Electric behavior of an inductor (2'32"): it is 
highlighted the current lag in relation to voltage, 
caused by an inductor connected to a sinusoidal 
voltage source; 
(14) Electrical behavior of inductor and capacitor in 
series (2'47"): analysis of the variation of current lag 
in relation to voltage, caused by a capacitor and an 
inductor connected in series to a sinusoidal voltage 
source with adjustable frequency; 
(15) Magnetic fields (7'12"): different experiments 
related to magnetic fields highlight the induction 
phenomenon (Faraday’s law of induction); 
(16) Residential electrical connections (3'00"): 
addresses the residential connections in electricity 
distribution;  
(17) Simple switch (2'43"): it is highlighted the 
correct connection of the simple switch used to trigger 
one or more fixtures from a single location; 
(18) Parallel switch (3'17"): it is highlighted the 
correct connection of parallel switches used to trigger 
two or more fixtures from two locations; 
(19) Intermediate switch (4'05"): it is highlighted 
the correct connection of the intermediate switch with 
parallel-type switches used to trigger one or more 
fixtures from three or more locations; 
Basic Concepts for Alternating Current through Educational Videos 
 
916
(20) Direct current motor-operation (5'19"): 
presentation of a device to trigger a direct current 
motor with starting current limitation and protective 
mechanism against excessive acceleration; 
(21) Induction motor-principle of operation (5'05"): 
it is presented the working principle of a three-phase 
induction motor through simple assembly; 
(22) Induction motor-operation-star-triangle switch 
(5'05"): explanation of the role of a star-triangle 
switch in a three-phase induction motor; 
(23) Transformer-principle of operation (5'10"): the 
working principle of a transformer is presented 
through simple assemblies; 
(24) Improved power factor (3'08"): we can see the 
benefits of improved power factor through capacitors 
in parallel connection to a single-phase induction 
motor; 
(25) Polarity of transformers (2'53"): easy method 
to identify the polarities of the terminals in a 
single-phase transformer;  
(26) Brazilian Standard 14136 (NBR14136) 
switches and plugs (2'40"): description of the switches 
standardized by ABNT (Brazilian Association of 
Technical Standards); 
(27) Single phase transformers in parallel (3'41"): a 
practical way of associating two single-phase 
transformers in parallel; 
(28) Obtaining active and reactive powers on a 
three-phase motor (2'53"): easy procedure to obtain 
three-phase active and reactive power on a three-phase 
induction motor; 
Note: the brackets information, for example, (5'01") 
for electric motors video, corresponds to the duration 
in minutes and seconds. The filming done so far 
totalizes 1 h 48 min 20 s. 
As can be seen, the videos produced are of short 
duration (up to 7 min.) and to ease access, they are 
available on YouTube (www.youtube.com) for being 
a popular site of videos, and they can be located using 
the acronyms ET016, ET616, UNICAMP or FEEC. 
3. Methodology 
The equipment used in the initial filming was a 
Nikon CoolPix 7600 7.1 megapixels Digital Camera 
and currently, we use a camcorder with high definition 
resolution, resulting in better picture quality and 
sound, for example, in the video behavior electric of 
RLC series circuit. 
Aiming to facilitate the topics understanding, in 
some of the videos we added figures, electric 
diagrams and formulas, both during and after their 
shoot. 
The final edit of the video was done with Windows 
Movie Maker, which shows educational videos can be 
possible at low cost. 
4. Results 
The receptivity of these videos can be accessed 
through the amount of views presented in Table 1 (by 
December 2013), surpassing a total of 654,000 related 
videos, the site of educational content 
(https://www.youtube.com/user/gilmarbarreto/). There 
were 1,080,515 views, as well as several publications 
in national and international conferences and the 
preparation of a textbook for a course in alternating 
current circuits [9-13]. 
This initiative has been rewarding due to the 
significant amount of comments on the videos content 
and also their didactic presentation, which has been a 
constant on incoming messages, some of which we 
reproduce below: 
“I am an electronics technician; I find it very 
interesting these matters, congratulations for the 
explanation, teacher!” 
“Excellent video, Greetings from Colombia!” 
“Awesome. It is the type of video I like to watch. I 
recommend bettering the audio next time, including 
subtitles in Spanish.”  
“This video is amazing. I think it should have more 
of this level.” 
“Congratulations, Gilmar! It is easy to learn from 
your teaching method, thanks for the video.” 
Basic Concepts for Alternating Current through Educational Videos 
 
917
Table 1  Number of views until December 2013. 
Characteristic curves of dipoles 2,406 
Concept of effective value 12,089 
RC series circuit 86,214 
RL series circuit 13,751 
RLC series circuit 38,927 
Three-phase load in unbalanced star 16,594 
Three-phase voltage 11,331 
Power factor correction 23,939 
Electric motors 14,310 
Determination of dipole resistance value 943 
Effective value-experimental procedure 1,409 
Electrical behavior of a capacitor 509 
Electrical behavior of a RL series circuit 1,293 
Electrical behavior of a RLC series circuit 6,146 
Magnetic fields 6,278 
Residential electrical connections 72,822 
Simple switch 35,752 
Parallel switch 114,837 
Direct current motor-starting protection 7,448 
Induction motor-principle of operation 29,209 
Induction motor-operation- star-delta-triangle 4,279 
Transformer-principle of operation 55,245 
Improving power factor  1,078 
Polarity of transformers 52,695 
ABNT NBR 14136 switches and plugs 1,871 
Single-phase transformers in parallel 3,295 
Obtaining active and reactive powers on a 
three-phase motor 
494 
 
“Thank you for that tip, it was very good.” 
“Excellent!!” 
“The material will be useful to review the concepts 
learned in my course.” 
“Very good teaching. I confess I did not know 
about that.” 
“It helped me a lot, it solved several questions. I 
admire a lot the work of Prof. Barreto. I read his thesis 
on building an electric vehicle and I confess it was one 
of the best materials I’ve ever encountered to date, the 
details and techniques presented are fantastic.” 
“I would like to know if I could have access to the 
course material, as it is essential for my activities at 
work.” 
“Very good, this video explains well the motor 
operation.” 
“I have never seen a better explanation. For a long 
time, I have been looking for something that explained 
in detail the operation of this engine and no material 
explained in this way.” 
“I thank you in advance for your attention and take 
this opportunity to congratulate you for the excellent 
organization of this material.” 
We are aware that these videos are being adopted as 
teaching material in other universities and technical 
schools, as well as being used in other websites which 
we have no control of access. 
TELEDUC is a web platform for implementation of 
courses (subjects) on the Internet with the purpose of 
distance learning and it has helped us in contact with 
students and the dissemination and use of teaching 
materials, in addition to regular classes. In Ref. [8], 
there is a master’s thesis in which we analyzed the 
students’ feelings with respect to this tool as didactic 
support in electrotechnical teaching. 
4. Final Consideration 
Through the work carried out until now, we found 
that we can use nonprofessional filming equipment 
and software easily to manipulate, as is the Windows 
Movie Maker case to produce excellent results in 
terms of production of educational videos, thus 
contributing to the improvement of teaching and 
knowledge dissemination. 
The videos meet students’ claim to facilitate 
electrotechnical theory understanding, since it deals 
with practical aspects and the subject does not include 
laboratory classes. 
The contribution to teaching and learning through 
the videos can be seen by an improvement in students’ 
performance on assessments in both test and exercises 
and comments from several university professors and 
technical schools that use the videos produced. 
The knowledge disseminated is serving our students, 
and other educational institutions can review many 
times a particular concept in basic electricity. The 
videos and their way of dissemination create 
Basic Concepts for Alternating Current through Educational Videos 
 
918
conditions for better learning, more quickly and to a 
greater number of students with the advantage of 
being able to watch the experiments at any time and 
review the subject through audiovisual resources. 
Other videos will be developed covering topics 
such as: 
 Faraday’s law; 
 Lenz’s law; 
 Construction of phasor diagrams; 
 Calculation of capacitors for power factor 
correction; 
 Blondel’s theorem; 
 Measurement of reactive power; 
 Safe electrical installation. 
We will also remake videos that are not in high 
resolution, e.g., electrical behavior of RLC series 
circuit. 
The preparation of educational videos by teachers 
and/or students to disclose knowledge and motivate 
learning is something that should be encouraged and 
supported. 
Acknowledgments 
The authors have relied on the effective support of 
the School of Electrical and Computer Engineering of 
University of Campinas, FEEC-UNICAMP that always 
encouraged us in the development of undergraduate 
teaching activities. Our gratitude is also to the Student 
Support Service-SAE, UNICAMP agency that manages 
the grants work for undergraduate students who have 
supported us in the preparation of these videos. 
References 
[1] Montessoro, P. L., and Caschi, S. 1999. “MTEACH: 
Didactic Multimedia Production.” Presented at the IEEE 
International Conference on Multimedia Computing and 
Systems, Florence, Italy. 
[2] Pullen, J. M. 2001. “Applicability of Internet Video in 
Distance Education for Engineering.” Presented at the 
31st ASEE/IEEE Frontiers in Education Conference, 
Reno, Nevada, USA.  
[3] Hailey, D. E., and Hailey, C. E. 2002. “Genre Theory, 
Engineering Education, and Circumventing Internet 
Bandwidth Problems.” Presented at the 32nd ASEE/IEEE 
Frontiers in Education Conference, Boston, 
Massachusetts, USA. 
[4] Gregory, J., and Strukov, A. 2002. “Utilization of Video 
Conferencing over the Internet to Facilitate Biological 
Education and Research at the University of Maine.” in 
Proceedings of International Conference on Computers 
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[5] Cai, L., and Yang, Y. 2004. “A New Idea of E-Learning: 
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[6] Amorim, J. A. 2005. “Engineering Education: The 
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[7] Osawa, N., Asai, K., Shibuya, T., Noda, K., Tsukagoshi, 
S., Noma Y., and Ando, A. 2005. “Three-Dimensional 
Video Distance Education System between Indoor and 
Outdoor Environments.” Presented at the 6th 
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University of Jordan. 
[8] Castilho, R. A. F. 2005. “The Incorporation of Virtual 
Learning Environments in Higher Education. A Study at 
the State University of Campinas.” Master thesis, State 
University of Campinas. 
[9] Barreto, G., and Murari, C. A. F. 2008. “Videos of 
Didactic Experiments for Learning in Electrical 
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[10] Barreto, G., and Murari, C. A. F. 2008. “Instructional 
Videos about Basic Concepts in Alternating Current 
Circuits.” Presented at the Brazilian Congress on 
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[11] Barreto, G., Miguel, P. V. O., and Murari, C. A. F. 2009. 
“Learning the Basic Concepts in Alternating Current 
Circuits through Youtube.” in Proceedings of IADIS 
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[12] Barreto, G., Murari, C. A. F., and Miguel, P. V. O. 2010. 
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2012. “Alternating Current Circuits-Fundamentals and 
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