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Formative assessment questions for teaching physics

A2L Item 221

  • Description: Identify the correct comparison between the voltages at two different points in a circuit.
  • Goal: Reason regarding circuits
  • Source: 283-560 Circuit voltages
  • Keywords: Voltage, Electromagnetism, Circuits

The question for students:

Consider the circuit below. How does the voltage difference between points A and C compare to the voltage difference between points A and D?

Item221_fig1.gif

  1. VAC < VAD

  2. VAC = VAD

  3. VAC > VAD

  4. Cannot be determined

Commentary for teachers:

Answer

(2) It is interesting to find out how many students recognized that the comparison did not require the use of Ohm’s law. To gauge student understanding it is interesting to ask questions such as; does any current flow in the wire between C and D? If C and D are at the same potential, why does any current flow?