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Sunday, February 12, 2012

Circuit misconceptions

Jacobs Physics blog bring us a post about Circuit Misconceptions

On a problem set last week, I gave students the simple circuit shown to the right. I asked what would happen to various parts of the circuit when I decreased R2. One of the questions in particular said, "What will happen to the current flowing from the battery when the value of R2 is decreased?"
The most common answer:

"The current will not change, because it's the same battery, so it will always provide the same current."
Silly students, a battery provides a constant VOLTAGE, not a constant current -- but that's a common misconception in the first week of circuits.
The second most common answer:

"The current will not change, because R2 is the farthest resistor from the battery, and so the current hasn't reached R2 yet.

(click here to read entire article and see how Mr. Jacobs solve the students' misconception)

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