Problem 4: who is right?Two parallel, infinite planes of charge have charge densities +20 and -o as shown in Fig. 1 They areat a distance L, from each other. Three students are asked to determine the electric field at points Aand B, at a distance L above the top plane, and at a distance L below the bottom plane, respectively, asshown in the figure. Each student comes up with a different answer and a different explanation. Readcarefully their statements below.The students are reminded that the electric field magnitude of an infinite plane of charge with chargedensity a is E = .+263+26Figure 1: Two cquivalent views of the two infinite parallel planes• Student 1 draws the sketch in Fig. 2 [top] and says: "I think from the outside we can think of thetwo planes as a single infinite plane with charge density +20 - o =0, so then we know the electricfield must be a/(2) pointing upwards at point A and also o/(2c) pointing doumwards at B".• Student 2 draws the sketch in Fig. 2 middle and says "I don't agree with you, I think you needto consider the effect of each single plane, so at point A there will be a field upwards due to thetop plane with magnitude 20/(2eo) = a/eo, and at point B there will be a field upwards due to thebottom plane with magnitude a/(2eo)"• Student 3 draws the sketch in Fig. 2 bottom) and says "Do we just add the electric fields together?I'm going to add up the field from each plane at both points. So at A I get a field upward ofmagnitude a/eo +a/(2eo) = 30/(2ro), and at point BI get the same 30/(2eo) but now pointingdownward"Evaluate each student's statement. Decide whether or not the statement is correct. If thestudent explanation contains incorrect reasoning, explain how the argument is flawed.studats11111 1&.student 2student 3½ up%3D3, downFigure 2: Students' sketches.blue口-

Student 3 is right in calculating the field as well as direction

Problem 4: who is right? Two parallel, infinite planes of charge have charge densities +20 and -o as shown in Fig. O They are at a distance Lo from each other. Three students are asked to determine the electric field at points A and B, at a distance L above the top plane, and at a distance L below the bottom plane, respectively, as shown in the figure. Each student comes up with a different answer and a different explanation. Read carefully their statements below. The students are reminded that the electric field magnitude of an infinite plane of charge with charge density o is E = +26 +26 Figure 1: Two equivalent views of the two infinite parallel planes • Student 1 draws the sketch in Fig. 2 (top) and says: "I think from the outside we can think of the two planes as a single infinite plane with charge density +20 - oa =a, so then we know the electric field must be a/(2o) pointing upwards at point A and also a/(2co) pointing dounwards at B". • Student 2 draws the sketch in Fig. 2 (middle and says "I don't agree with you, I think you need to consider the effect of each single plane, so at point A there will be a field upwards due to the top plane with magnitude 20/(2ro) = a/ea, and at point B there will be a field upuards due to the bottom plane with magnitude a/(2o)". • Student 3 draws the sketch in Fig. 2 bottom and says "Do we just add the electric fields together? I'm going magnitude a/ea +a/(2eo) = 30/(2ro), and at point BI get the same 30/(2eo) but now pointing dounward" add up the field from each plane at both points. So at A I get a field upward of Evaluate each student's statement. Decide whether or not the statement is correct. If the student explanation contains incorrect reasoning, explain how the argument is flawed. studets 1%. 국 +936-6) student 2 studeut 3 % up +1 = 32 down Figure 2: Students' sletches.