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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
Student’s Alternative Conception in Basic Electric Circuit
Noor Hamizah Hussain
Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
[email protected]
Kamilah Radin Salim, Habibah Norehan Haron, Rosmah Ali
Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
[email protected], [email protected], [email protected]
Habsah Hussain
Politeknik Sultan Abdul Halim Mu'adzam Shah (POLIMAS), Kedah, Malaysia
[email protected]
Abstract: The goal of this work-in-progress is to investigate alternative conceptions held
among students about an open and short circuit concepts involving current, voltage and
resistors. This study was carried out in Malaysia and involved first-year Electrical
Engineering students. Students’ pretest and posttest answers to concept test were
analyzed. The teaching and learning strategies were the traditional lecturing style using
white-board and PowerPoint presentation. Interview was conducted to investigate about
their conceptual understanding. Results showed that student’s held very strong
alternative conceptions on the concepts tested. This finding will be useful in developing
and implementing new teaching and learning activities or adapting available ones to
assist their conceptions.
Introduction
Many studies have been concentrated on investigating alternative conceptions held by engineering
students (Ogunfunmi and Rahman, 2010; Prince, Vigeant and Nottis, 2010; Smaill et al., 2011)
especially in Mechanical, Electrical and Chemical Engineering. Learning conceptual knowledge is a
critical element in the development of competence and expertise in engineering (Streveler et al.,
2008). It is common for lecturers to overestimate the degree to which students understand concepts
(Engelhardt and Beichner, 2004; Smaill et al., 2011; Streveler et al., 2006).
Streveler et al. (2006) has identified 27 items of concepts that are important to learn in Electric
Circuits but students find it difficult to grasp. This research investigated further into three items from
the list namely equivalent resistances, interpretation of circuit diagrams and Thevenin/Norton
equivalent circuits (Streveler et al., 2006); and also by introducing concept test to the course
investigated (Ogunfunmi and Rahman, 2011; Sabah, 2007; Smaill et al., 2011).
Based on preliminary studies, students are found to bear misunderstanding in solving circuit to obtain
the current, voltage and resistance for both Norton and Thevenin theorems (Hussain, Latiff and
Yahaya, 2009). The underlying concepts investigated in this research are open and short circuit
concepts. Therefore this study investigated the alternative conception held by students in grasping
open and short circuit concepts.
Methodology
The samples are 47 first-year students enrolled in Diploma in Electrical Engineering program in
Malaysia. The study was conducted during the second semester of their study where they have
completed the Electric Circuits course in their first semester.
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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
Data were collected through concept test and interviews. The concept test questions were adapted
from Sabah (2007) which was based on Engelhardt (1997) and Engelhardt and Beichner (2004). The
12 questions concept test was used in the pretest and posttest. The switches are used in the electric
circuit questions to create the conditions of open and short circuit. The pretest was administered
during the first week after the semester began. However, for the purpose of this paper, only three
questions will be discussed and analyzed namely question 1, 5 and 9.
The teaching and learning strategies were traditional lecturing using white-board and PowerPoint
presentation. The posttest was administered during the final week before the semester ends.
Interview sessions were conducted in groups of three to four students. Students were interviewed
where they had to explain their reasoning about questions that they had answered wrongly.
Results and Discussion
Students’ responses to the pretest and posttest were tabulated in the tables. The shaded row shows the
correct answer. The marks obtained from pretest and posttest was analyzed with SPSS using pairedsample t-test. The data obtained from interview were analyzed qualitatively to find students’
alternative conceptions on open and short circuit. The interviewed data is quoted based on coding as
R is for researcher and S is for students.
1.
Simple Circuit
Question 1 as shown in Figure 1 required students to consider the current flowing through the circuit.
1.
Compare the current at point 1 with the current at point 2. Which point has a larger current?
a.
b.
c.
1
Point 1.
Point 2.
They are the same
R
R
12 V
R
2
Reason:
a.
b.
c.
d.
Current travels in two directions around the circuit.
Current from the battery goes to the circuit and then comes back to the battery.
The resistors use up a little of the current.
Others (Please specify): _________________________________________
Figure 1: Question 1
Table 1 shows the data obtained from students answer.
Table 1: Students’ response to Question 1
% Students’ Answer &
Reasons
Answer & Reason
% Pretest Response
% Posttest Response
ac
cb
8.5
63.8
6.4
76.6
Concept Tested in Q1
Circuit must be complete for current to conduct.
Analysis of Response
This circuit is a complete simple circuit and has asked for current flowing in a
complete circuit. There are 63.8% and 76.6% of students’ understand the
concept of current flowing.
Table 1 shows that 63.8% responded correctly for pretest, and increased to 76.6% in the posttest.
However students (8.5% in pretest and 6.4% in posttest) who answered a (point 1) and reasoned c (the
resistors use up a little of the current), relied on the alternative conception that the current is
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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
consumed by and sink at the resistors in the circuit (Engelhardt, 1997; McDermott, 1996). This
conclusion was made based on interview data as quoted below.
R:
S1:
R:
S1:
S2:
Can you explain which point has the higher current?
Point 1
Why point 1?
Because the current has not taken up by any R yet
Yes, I have the same reason as her.
R:
S3:
You said point 1 has higher current, can you explain your reason why?
I thought the current has to divide into two, because of parallel, therefore the current coming
out is less.
S1 and S3 understanding was point 1 has higher current than point 2 because the resistor consumes a
little current. The conclusion that can be made is that students do analyze circuits with sequential
reasoning as claimed by Engelhardt and Beichner (2004), analyzing one element after the other; rather
than taking the circuits as a whole (Smaill et al., 2011). Such students believed that current travels
around a circuit and are influenced by each element as it is encountered (Engelhardt and Beichner,
2004; Smaill et al., 2011). Students who gave reason c (the resistors use up a little of the current)
confused about the concept of the resistor and current in a circuit.
Data analyzed using paired-sample t-test was shown in Table 2.
Table 2: Paired-sample statistics to Question 1
Test
Posttest
Pretest
N
47
47
Mean
1.70
1.66
Standard Deviation
0.657
0.668
p
0.743
From Table 2, there is significant evidence that their mean are not the same with the gain difference
of 0.07. However the probability value p > 0.05 gave no significant improvement from pretest to
posttest in understanding current flowing in simple circuits.
2.
Open Circuit
Question 5 required students to consider the operation of the circuit after the switch is closed.
5.
How does the resistance between the terminal A and B change when the switch is closed?
a.
b.
c.
d.
e.
Reason:
a.
b.
c.
d.
Increase by R/2
Increase by R
Stay the same
Decrease by R/2
Decrease by R
R
R
Switch
A
B
R
Closing the switch will add a resistor in series.
The circuit is not affected after closing the switch.
Adding a resistance in parallel to any branch decreases its total resistance.
Others (Please specify): _________________________________________
Figure 2: Question 5
Table 3 shows the data obtained from students answer.
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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
Table 3: Students’ response to Question 5
% Students’ Answer &
Reasons
Answer & Reason
% Pretest Response
% Posttest Response
aa
ac
dc
8.5
10.6
53.2
8.5
10.6
46.8
Concept Tested in Q5
Adding or removing resistor will affect the value of total resistance.
Analysis of Response
This circuit asked for total resistance before and after closing a switch.
Only 53.2% and 46.8% understand the concepts of total resistance.
Table 3 shows that students confused about the effect of open and closed switch on the resistance in a
circuit. They have alternative conception about the resistor behavior.
The following were reasoning made by students to explain for their wrong answer where more indepth meaning of their conception was obtained.
R:
S8:
R:
S8:
When the switch is open, is the current flow to the top R?
No
So if the switch is open, what is the total R?
Hmmm open….open circuits, no current flow therefore no R.
R:
S1:
Which R is in this circuit if the switch is open?
I forgot about open and closed. During close circuits which R is active, which one is not…
R:
S3:
R:
S3:
R:
S3:
R:
S3:
R:
S3:
When the switch is open, is the current flow to the top R?
Hmmm not sure…
So is there any current flow at open branch?
No.
If there is no current, will the top R active?
No….
So what is the total R during open?
Is the lower R active during open?
Good question…think for a while
I am not sure….as I understand if the switch is open, the lower R also is inactive…therefore
only the first R left….
Based on interview data, six out of 15 students interviewed explained that they cannot understand the
effect of switch especially when determining the total resistance in an open circuit. Students are
confused about the function of switch. They perceived as opening the switch as disabling the whole
parallel arm, therefore no current flow to B; hence ignored both resistors in parallel. These concepts
of resistance, open and short were interrelated defining their alternative conception.
Data analyzed using paired-sample t-test was shown in Table 4.
Table 4. Paired-sample statistics to Question 5
Test
Posttest
Pretest
N
47
47
Mean
1.60
1.28
Standard Deviation
0.614
0.852
p
0.042
From Table 4, there is significant evidence that their mean are not the same with the gain difference
of 0.2. The probability value p <0.05 where p = 0.042 gave significant improvement from pretest to
posttest on concepts of resistors in open circuit.
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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
3.
Closed Circuit
Question 9 required students to consider the operation of the circuit when switch is closed.
9.
What will happen to the voltage between
Switch
2R
points A and B if the switch is closed?
a.
b.
c.
R
A
Increase
Decrease
Stay the same
B
12 V
Reason:
a.
b.
c.
d.
e.
The voltage is distributed between the resistors based on the value of the resistance.
Closing the switch will increase the total resistance of the circuit.
Adding 2R will decrease both the voltage across R and the current flowing through R.
Adding 2R resistor affects the battery current only.
Others (Please specify): _________________________________________
Figure 3: Question 9
Table 5 shows the data obtained from students answer.
Table 5: Students’ response to Question 9
% Students’ Answer &
Reasons
Answer & Reason
% Pretest Response
% Posttest Response
bc
cd
25.5
25.5
6.4
36.2
Concept Tested in Q9
Adding another branch in a parallel circuits will not affect the total voltage
Analysis of Response
This circuit asked for voltage in a circuit before and after closing a switch.
Only 25.5% and 36.2% understand the concepts voltage in a circuit.
Answer bc (25.5% from pretest and 6.4% from posttest) really shows students have surface
understanding on concept of parallel circuits which hinders their scientific conception. They have
convoluted understanding about the dependence of current on terminal voltage only, not the resistor
(Hussain, Latiff and Yahaya, 2012)
The following were reasoning made by students in explaining for their wrong answer where more indepth meaning of their conception was obtained.
R:
S9:
R:
S9:
What is the concept behind parallel circuits?
Same voltage
What is the reason?
I don’t know how to explain and give reasons.
R:
Can you explain to me why the voltage stays the same?
S13: I am confused. Is voltage stay the same or have to divide by 2 branches?
S5: I don’t know about the effect of R and 2R in this circuit….parallel circuits?
All the wrong answers given really showed their alternative conceptions where they cannot notice the
effect of open circuit on voltage and also on resistance. The finding can again be made that students
relied heavily on Ohm’s law, where they assumed current as the prime concept. This conclusion was
made based on interview data as quoted above.
Data analyzed using paired-sample t-test is shown in Table 6.
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Hussain N. H. et al., Student’s Alternative Conception in Basic Electric Circuit
Table 6. Paired-sample statistics to Question 9
Test
Posttest
Pretest
N
47
47
Mean
1.21
0.96
Standard Deviation
0.832
0.908
p
0.183
From Table 6, there is significant evidence that their mean are not the same with the gain difference
of 0.25. However the probability value p > 0.05 gave no significant improvement from pretest to
posttest in understanding the operation of the closed circuit.
Conclusions
Students’ responses to the concept test and interviews were analyzed to evaluate their alternative
conceptions on open and short circuit concepts in basic electric circuit course. The most significant
finding of the study is that student has an alternative conception of “when there is no current; there is
also no voltage; therefore, there is no resistance”; which shows students relied solely on Ohm’s Law
without having deep understanding of the concepts. Moreover, the paired-sample t-test results
showed that students made no improvement on their understanding of the concepts of current and
voltage in simple circuits and short circuits. These finding will be useful for future work in improving
the teaching and learning activities that could help assist students’ conception. The process of
developing and implementing the new teaching and learning activities will be discussed by the
authors in another paper.
References
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Copyright © 2013 Hussain, Radin Salim, Haron, Ali, Hussain: The authors assign to the REES organisers and educational
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