Physics Students’ Conceptual Understanding of Electricity and Magnetism in Nine Years Basic Education in Rwanda

We investigate students’ misconceptions in electrostatics, direct current (DC) and magnetism which are important in electricity and magnetism. We developed and administered a multiple-choice questionnaire test to reveal students’ misconceptions related to charged bodies, lightning, electric fields, electric potential, forces, DC resistive electric circuits and magnets. This test aimed at obtaining quantitative information about misconceptions and was administered to 380 senior two students from Nine Year Basic Education (9YBE) Schools. The selected students have some experience with the new Rwandan secondary physics Competence Based Curriculum (CBC) that is currently under implementation. We find that senior two students have several common misconceptions related to these concepts. The data indicate that although students have some backgrounds on the subject matter, they still seem to believe that if the two charges are separated by a distance, a large-charged object exerts a greater force of attraction or repulsion on the small one. Considerable number of participated students held the misconception of considering current consumption in the resistor/bulb or the electrical devices in the circuits. They also believed that the battery was a continuous current source. The findings also revealed that students held a misconception that a bar magnet when broken into pieces, it is demagnetized. Moreover, a considerable number of participants hold the misconception that all metals are attracted by a magnet. Our study also revealed some of the statistically significant differences in terms of either gender or location of schools for some items.

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Univariate and multivariate DMS calibration for a single analyte

E3S Web of Conferences ◽

10.1051/e3sconf/201910000078 ◽

2019 ◽

Vol 100 ◽

pp. 00078

Author(s):

Andrzej Szczurek ◽

Monika Maciejewska ◽

Żaneta Zajiczek

Keyword(s):

Electric Fields ◽

Gas Flow ◽

Chemical Warfare Agents ◽

Calibration Procedure ◽

Quantitative Information ◽

Multivariate Approach ◽

Least Squares Regression ◽

Differential Mobility ◽

Mobility Spectrum ◽

Warfare Agents

Differential mobility spectrometry (DMS) is a promising measurement technique. It is used in the detection of chemical warfare agents, explosives, drugs, and volatile organic compounds. The measurement principle is based on separation of gas-phase ions according to their differential mobility in alternating low and high electric fields. The DMS measurement result is a two dimensional spectrum of ion current displayed as a function of separation voltage and compensation voltage. The DMS spectral peaks, in terms of their height, location and width, are affected by gas sample composition, separation field and the gas flow rate. In this work, there is presented the calibration procedure which utilises the univariate and multivariate approach to differential ion mobility spectrum. We demonstrated the possibility of a successful retrieval of quantitative information using partial least squares regression as well as univariate linear regression. However, the multivariate approach outperformed the univariate one in terms of the quality of the model and the concentration prediction accuracy.

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Continuous current source driver

High Frequency MOSFET Gate Drivers: Technologies and Applications ◽

10.1049/pbcs033e_ch3 ◽

2017 ◽

pp. 45-101

Keyword(s):

Current Source ◽

Continuous Current

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Continuous current source inversion of evoked potential fields in a spherical model head

IEEE Transactions on Biomedical Engineering ◽

10.1109/10.335836 ◽

1994 ◽

Vol 41 (11) ◽

pp. 997-1003 ◽

Cited By ~ 14

Author(s):

R. Srebro

Keyword(s):

Evoked Potential ◽

Current Source ◽

Spherical Model ◽

Potential Fields ◽

Source Inversion ◽

Continuous Current

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Adaptive continuous Current Source Drivers to achieve efficiency improvement in wide load range

2011 IEEE Energy Conversion Congress and Exposition ◽

10.1109/ecce.2011.6063912 ◽

2011 ◽

Cited By ~ 4

Author(s):

Zhiliang Zhang ◽

Wei Cai ◽

Pengcheng Xu

Keyword(s):

Current Source ◽

Efficiency Improvement ◽

Load Range ◽

Continuous Current

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PROEJA E As REPERCUSSÕES SOBRE A ESCOLARIZAÇÃO DE BENEFICIÁRIOS

Revista Políticas Públicas ◽

10.18764/2178-2865.v24n2p912-930 ◽

2020 ◽

Vol 24 (2) ◽

pp. 912

Author(s):

Edinolia Lima Portela

Keyword(s):

Adult Education ◽

Professional Education ◽

Basic Education ◽

Quantitative Information ◽

Educational Programs ◽

National Program ◽

Contextual Variables ◽

Qualitative And Quantitative ◽

Federal Institute ◽

Research Tools

Pesquisa social de natureza avaliativa baseada em informações qualitativas e quantitativas. Estuda o Programa Nacional de Integração da Educação Profissional com a Educação Básica na Modalidade de Educação de Jovens e Adultos - Proeja, desenvolvido pelo Instituto Federal do Maranhão (Ifma/ Campus Maracanã), entre os anos 2015/2017, com o objetivo deavaliar as implicações do programa na vida dos egressos, focalizando a continuação dos seus estudos. Fundamenta-se à luz do pensamento de Minayo (1991), Sposito (2005) e Arendt (2009). Além disso, debruça-se sobre as orientações do documento que baliza o Proeja. Participaram da pesquisa 79 egressos e utilizaram-se, como instrumentais de pesquisa, aentrevista aberta e o questionário. Os resultados revelam que, a despeito das inúmeras variáveis contextuais, o Proeja contribuiu para o prosseguimento dos estudos dos egressos.Palavras-chave: Egressos do Proeja. Problemática de jovens e adultos trabalhadores. Resultado de programas educativos. Jovens e adultos e escolarização.PROEJA AND THE REPERCUSSIONS ON THE SCHOOLING OF BENEFICIARIESAbstractSocial research of an evaluative nature, based on qualitative and quantitative information. It studies the National Program for the Integration of Professional Education with Basic Education in the Youth and Adult Education Mode -Proeja, developed by the Federal Institute of Maranhão (Ifma) - Campus Maracanã, between the years 2015/2017, with the objective of evaluatingthe implications of the program in the life of the egresses., focusing on the continuation of their studies. It is based on the thought of Minayo (1991); Sposito (2005) and Arendt (2009). In addition, it focuses on the guidelines of the Document that guides Proeja. 79 graduates participated and the open interview and the questionnaire were used as research tools. The results of the research reveal that, in spite of the innumerable contextual variables, Proeja contributed to the continuation of the studies of the graduates.Keywords: Graduates of Proeja. Issues of young and adult workers. Result of educational programs. Youth and adults and schooling.

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Electrochromism of Viologen/Polymer Composite: From Gel to Insulating Bulk for High-Voltage Applications

Materials ◽

10.3390/ma14195901 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5901

Author(s):

Yongjie Nie ◽

Meng Zhang ◽

Yuanwei Zhu ◽

Yu Jing ◽

Wenli Shi ◽

...

Keyword(s):

Power Systems ◽

Space Charge ◽

Electric Fields ◽

High Voltage ◽

Vinylidene Fluoride ◽

Power Equipment ◽

Charge Accumulation ◽

Charge Detection ◽

Continuous Current ◽

High Electric Fields

Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of great demand in the power industry. Typical electrochromic phenomenon is based on redox of the material, triggered by a voltage smaller than 5 V with a continuous current in μA~mA level, which is not applicable to high electric fields above 106 V/m with pA~nA operation current in power equipment. Until now, no naked-eye observation technique has been realized for space charge detection to ensure the operation of power systems as well as the safety of maintenance workers. In this work, a viologen/poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF–HFP)) composite is investigated from gel to insulating bulk configurations to achieve high-voltage electrical-insulating electrochromism. The results show that viologen/P(VDF–HFP) composite bulk can withstand high electric fields at the 107 V/m level, and its electrochromism is triggered by space charges. This electrochromism phenomenon can be visually extended by increasing viologen content towards 5 wt.% and shows a positive response to voltage amplitude and application duration. As viologen/P(VDF–HFP) composite bulk exhibits a typical electrical insulating performance, it could be attached to the surface of insulating structures or clamped between metal and insulating materials as a space charge accumulation indicator in high-voltage power equipment.

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Three‐dimensional terrain corrections for mise‐à‐la‐masse and magnetometric resistivity surveys

Geophysics ◽

10.1190/1.1441579 ◽

1984 ◽

Vol 49 (10) ◽

pp. 1718-1729 ◽

Cited By ~ 23

Author(s):

G. L. Oppliger

Keyword(s):

Surface Charge ◽

Charge Distribution ◽

Electric Fields ◽

Current Source ◽

Three Dimensional ◽

Solution Technique ◽

Surface Integral ◽

Surface Charge Distribution ◽

Terrain Corrections ◽

Subsurface Current

Three‐dimensional modeling of topographic effects in mise‐à‐la‐masse and magnetometric resistivity surveys is accomplished using the surface integral equation method. The technique provides a means for (1) analyzing these effects on earth models of homogeneous conductivity; and (2) removing terrain effects from field data. A new method combining current source images with surface charge is developed to treat the electric field boundary conditions at the air‐earth interface. The method uses an image of each subsurface current source positioned above the surface, so as to induce a surface charge distribution which approximately cancels the charge distribution induced by the subsurface current source. The resulting residual surface charge distribution varies spatially more gradually than either of the original charge distributions, and hence may be represented accurately on a coarsely segmented model surface with simple basis functions. The topographic surface is modeled by a finite number of facets, each with constant slope and surface charge density. Charge values are obtained with an iterative solution technique. Surface electric fields are calculated from the surface charge distribution, current sources, and images. The magnetic field is found by evaluating a surface integral involving surface slopes and electric fields. The numerical solution is verified by comparisons with dipole‐dipole resistivity results from a two‐dimensional finite‐element model of a valley, and with analytic solutions for the magnetic fields over a dipping interface. Methods for terrain correcting mise‐à‐la‐masse and magnetometric resistivity data are demonstrated with examples using actual field measurements. The results of this study show that (1) rugged topography can significantly distort measurements in mise‐à‐la‐masse and magnetometric resistivity surveys; and (2) the described modeling technique provides an effective means of calculating terrain corrections for both the mise‐à‐la‐masse and magnetometric resistivity methods over complex three‐dimensional topography.

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Stark spectroscopy of mixed-valence systems

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2007.2137 ◽

2007 ◽

Vol 366 (1862) ◽

pp. 33-45 ◽

Cited By ~ 12

Author(s):

Lisa N Silverman ◽

Pakorn Kanchanawong ◽

Thomas P Treynor ◽

Steven G Boxer

Keyword(s):

Charge Transfer ◽

Electric Fields ◽

Dipole Moments ◽

Mixed Valence ◽

Quantitative Information ◽

Stark Spectroscopy ◽

Charge Transfer Transition ◽

Band Position ◽

Stark Effects ◽

Intervalence Charge Transfer

Many mixed-valence systems involve two or more states with different electric dipole moments whose magnitudes depend upon the charge transfer distance and the degree of delocalization; these systems can be interconverted by excitation of an intervalence charge transfer transition. Stark spectroscopy involves the interaction between the change in dipole moment of a transition and an electric field, so the Stark spectra of mixed-valence systems are expected to provide quantitative information on the degree of delocalization. In limiting cases, a classical Stark analysis can be used, but in intermediate cases the analysis is much more complex because the field affects not only the band position but also the intrinsic bandshape. Such non-classical Stark effects lead to widely different bandshapes. Several examples of both classes are discussed. Because electric fields are applied to immobilized samples, complications arise from inhomogeneous broadening, along with other effects that limit our ability to extract unique parameters in some cases. In the case of the radical cation of the special pair in photosynthetic reaction centres, where the mixed-valence system is in a very complex but structurally well-defined environment, a detailed analysis can be performed.

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