A2L Item 208

• Description: Identify points around a physical dipole having zero electric field.
• Goal: Hone the concept of electric field
• Source: 283-340 Where is E zero near a dipole? 9/21
• Keywords: Electric Field, Electromagnetism

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The question for students:

Where, other than at infinity, is the electric field 0 in the vicinity of the dipole shown?

1. Along the y-axis.
2. At the origin.
3. At two points, one to the right of (a, 0), the other to the left of (-a, 0).
4. At two points on the y-axis, one below the origin, one above the origin.
5. None of the above.

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Commentary for teachers:

Answer

(5) Students have a lot of difficulty distinguishing electric field from potential. Students already exposed to the concept of potential frequently respond that the field is zero along the y-axis. If there are many confused students, before identifying the correct response, it helps to have the students draw the field lines.

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