Was there a mistake in our final exam question about resistance?

Thread starter Eitan Levy
Start date Jun 29, 2018
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Exam Final Mistake Resistance

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SUMMARY

The forum discussion centers on the interpretation of resistance in a physics exam question, specifically regarding the calculation of resistance using the formula R=ΔV/ΔI when the voltage-current graph does not pass through the origin. Participants assert that while Ohm's Law (V=IR) applies to linear resistors, the formula R=ΔV/ΔI is valid for non-linear components, where resistance varies with voltage. The conversation highlights the distinction between chordal resistance (V/I) and differential resistance (dV/dI), emphasizing the need for clarity in exam questions regarding these concepts.

PREREQUISITES

Understanding of Ohm's Law (V=IR)
Familiarity with the concepts of chordal resistance and differential resistance
Knowledge of voltage-current (V-I) characteristics of resistors
Basic principles of non-linear circuits

NEXT STEPS

Research the differences between chordal resistance and differential resistance
Study non-linear circuit behavior and its implications on resistance calculations
Examine real-world applications of differential resistance in electronic components
Review common pitfalls in interpreting physics exam questions related to resistance

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Physics students, educators, and anyone involved in teaching or learning about electrical resistance and circuit theory will benefit from this discussion.

Jul 1, 2018

CWatters

Science Advisor

Homework Helper

Gold Member

Eitan Levy said:

In the answers only one answer was given.

In which case I'd want to see the exact wording of the question. At the very least it's unclear in the OP.

You could try writing to the examining board but most won't enter into correspondence. I'd be tempted to find a forum for professional electrical/electronic engineers in your country and post the question there. Dont post the answer initially, just see what replies you get. Perhaps see if you can't interest them in writing to the board to complain about the quality of the question.

Here in the UK the correct answer for this in a GCSE Plysics exam (taken at age 16) would be the range of values given by R=V/I.