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# AS Physics Tricky Question watch

1. How does the tension affect resistance of a wire?

Do we have to use resistivity equation and maybe plot a graph I really don't get it
2. When a wire is stretched, assuming you have the same length of unstretched wire, the cross sectional surface area of the wire decreases. As a result, the resistance of the stretched wire will be higher because the CSA is less. Just a thought, hope that helps!
3. (Original post by ChipDeeks)
When a wire is stretched, assuming you have the same length of unstretched wire, the cross sectional surface area of the wire decreases. As a result, the resistance of the stretched wire will be higher because the CSA is less. Just a thought, hope that helps!
Surely Length of a stretched wire will eventually increase right? Since you stretch it, it won't stay the same so length will increase and Cross-sectional area will decrease and resistivity stays the same but still I don't know how to do a proper experiment on this
4. Well, if you're wanting to know how tension changes resistance like you said then I think what I said is right, but if you're talking about resistivity, then I'm not quite sure..... Are length and CSA directly proportional? Because then, if not, resistivity will change if it's stretched. Not quite sure if that makes sense though. :/
5. (Original post by ms94uk)
How does the tension affect resistance of a wire?

Do we have to use resistivity equation and maybe plot a graph I really don't get it
It's strain (the change in the shape) that affects resistance.
If you stretch a wire it gets longer and thinner.
The formula

tells you how a change in l and A affect R

(resistivity) itself doesn't change but resistance does.
A strain gauge (look it up on Google) uses this idea to measure strain.

Applying stress to a wire (placing it under tension) will cause strain.

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