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Resistance is futile

So I got myself a handgun. The purpose of me purchasing this vital tool is to shoot myself in the foot each and every time I make another silly mistake. That should teach my brain to function better.

So, this is the last question from Nov.2005 that gave me a little problem.
Check attachment.


This question is about resistance in a lquid. The graph shows the variation of I against V.

The question asked when is resistance the smallest. Now, since v = IR, then R = V/I = 1 / gradient (as the graph is I vs R).

So smallest resistance occurs at largest gradient. Now I perceive that largest gradient occurs at A.

But the mark scheme has choice C as the answer!!!
Isn't C a gentler gradient than A?


Thanks guys for all your help!
I have my handgun loaded.
Pointing at my right foot.
Hope I am not making a silly mistake.
resistance.doc33.8KB
No, smallest resistance occurs at the largest value of I/V, which is nothing to do with the gradient dI/dV. The latter gives you the gradient of the curve, the former gives you the gradient of the line from the origin to a point on the curve. OC is obviously steeper than OA, OB and OD...
Reply 2
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batboy
OP
generalebriety!
The physics forums was the last place on Earth I expected you to be.
This is why I asked what subjects you did - so from now on, if I have any dent's in my sphere of physics, I will pester you. LOL.

OOOOOOOOOOOOOOOOOOH!!!!!!!

I do remember reading a mark scheme where it stated to reject any argument about gradient or inverse of gradients.

Thanks for clarifying that up.
Now, I did not know that that was the way to figure it out. So it wasn't a silly mistake. Good. No leg shooting today.

I learnt a new technique today. Instead of gradients on the curve, draw a line from the origin for a better analysis of resistance.

Sweet.

How is the second oldest English speaking university of the world? Your folks must be real proud - I mean getting accepted to cambridge is no small feat.

Thanks generalebriety for the clarification
Reply 3
Avatar for batboy
batboy
OP
I just placed my mouse over your green bar next to the my societies.

A pop up says: generalebriety has too much reputation for his own good.

LOL.

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