\r\nelectrostatics. In high-school, generally Thai students have already

\r\nlearned about definition of electric field, electric field due to a point

\r\ncharge, and superposition of electric fields due to multiple-point

\r\ncharges. Those are the prerequisite basic knowledge students holding

\r\nbefore entrancing universities. In the first-year university level,

\r\nstudents will be quickly revised those basic knowledge and will be

\r\nthen introduced to a more complicated topic—electric field due to

\r\ncontinuous charged distributions. We initially found that our

\r\nfreshman students, who were from the Faculty of Science and

\r\nenrolled in the introductory physic course (SCPY 158), often

\r\nseriously struggled with the basic physics concepts—superposition of

\r\nelectric fields and inverse square law and mathematics being relevant

\r\nto this topic. These also then resulted on students’ understanding of

\r\nadvanced topics within the course such as Gauss's law, electric

\r\npotential difference, and capacitance. Therefore, it is very important

\r\nto determine students' understanding of electric field due to

\r\ncontinuous charged distributions. The open-ended question about

\r\nsketching net electric field vectors from a uniformly charged

\r\ninsulating rod was administered to 260 freshman science students as

\r\npre- and post-tests. All of their responses were analyzed and

\r\nclassified into five levels of understandings. To get deep

\r\nunderstanding of each level, 30 students were interviewed toward

\r\ntheir individual responses. The pre-test result found was that about

\r\n90% of students had incorrect understanding. Even after completing

\r\nthe lectures, there were only 26.5% of them could provide correct

\r\nresponses. Up to 50% had confusions and irrelevant ideas. The result

\r\nimplies that teaching methods in Thai high schools may be

\r\nproblematic. In addition for our benefit, these students’ alternative

\r\nconceptions identified could be used as a guideline for developing the

\r\ninstructional method currently used in the course especially for

\r\nteaching electrostatics.","references":null,"publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 109, 2016"}