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On 1/2/2015 4:21 PM, Robert Cohen wrote:
It is quite likely that students having problems with this are too
focused on the algebraic equation...Ohm's Law...without much
understanding of what the three quantities in that equation actually are.
I'd be careful to introduce and discuss current, resistance, and
voltage thoroughly before introducing Ohm's Law. I will have my
classes come up with an equation for the resistance of an object
through analogy and simple reasoning. They will even come up with
the idea of temperature dependency (which we then say we usually
ignore!) But at this point, sans the temperature component, the
resistance of a given object (yes, between two specified points) is
fixed by its geometry and material.
With that idea firmly in place, students may be less likely to try and
solve for the resistance as V/I and then be befuddled because they
don't know that the current is.
To be honest though, I've never actually used the question below in
quizzing, so not sure how my groups would have fared.
rwt
How about the following? Students frequently have trouble with it. An
ohmic resistor of resistance 10 ohms allows 1 A of current to flow
when a voltage of 10 V is applied across it. What is the resistance
of the SAME resistor when a voltage of 100 V is applied across it?
How would you help students who have difficulty with this question?
Philip Keller wrote:
They are already functioning at the edge, not completely convincedWhen formulating your answer, keep PK's quote in mind.
that thinking is a way to find things out.
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