A2L Item 150

• Description: Indicate the correct statement(s) regarding the work done moving a charge between to points having different electric potential.
• Goal: Link work and potential
• Source: 283-465 Interpreting voltage
• Keywords: Electromagnetism, Potentials, Work

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The question for students:

The potential at two points in space is: V₁=200 Volts, V₂=300 Volts. Which of the following statements is true for moving a point charge, q, from point 1 to 2?

1. The work done by an external agent to move q from point 1 to 2 is positive.
2. Can't determine the work done because you don't know the direction of V at the two points.
3. The work done by the electrical force exerted on q in moving it from point 1 to 2 is: W = -q(100 Volts).

1. A
2. B
3. C
4. A and B
5. A and C
6. A, B, and C
7. None of the above

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Commentary for teachers:

Answer

(3) is the best response. Statement A is true only if the charge is positive. The important thing is to see if students correctly envision the electric field lines as directed from higher potential to lower.

Any response involving statement B should be discussed thoroughly as it indicates confusion between fields and potentials.

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