Question

Hiii friends...!✌
I need urgent help... I've an exam today...Please answer the following questions with proper and complete explanations. NO COPYING AND NO IRRELEVANT ANSWERS REQUIRED.
1. The resistance of a wire is 20 ohm. It is so stretched that the length becomes three times, then the new resistance of the wire is?
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Sorry to say but now I realized that this app is of no help...;((
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Open my profile and see the latest questions...And solve if you can...
PLEASE

Answer 1

R=(ρ∗L)/AR=(ρ∗L)/A

If the wire is an isolated system (no extra metals/wires coming in or going out) with a specified length and cross-sectional area, then stretching it would increase the length 3 times and presumably reduce the cross-sectional area 3 times as well. Then,

R=(ρ∗3L)/(1/3∗A)R=(ρ∗3L)/(1/3∗A)

R=9(ρ∗L)/A)R=9(ρ∗L)/A)

You get 9 times more resistance you initially had, this makes sense as you bring the wire to a thinner cross-sectional area, the electrons have more material to go through.

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Answer 2

resistance= ro l/A

where ro is resistivity constant, l is length of wire and A is cross-sectional area

l2=3times of l1

since, l is directly proportional to resistance,

resistance is increased threefold

therefore resistance is  3 x 20 ohm = 60ihm

Hope this helps :)