Question

A piece of wire of resistance 20 ohm is drawn out as that its length is increased to twice its original length .calculate new resistance.And resistivity

Answer 1

Answer:

A piece of wire of resistance 20Ω is drawn so that its length is increased to twice is original length. Calculate resistance of the wire in the new situation. R=ρlA or 20Ω=ρlA. When the length becomes 2l and cross-sectional area is A/2.

Explanation:

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Answer 2

Answer:

Resistance depends upon length and area of cross section as ( given resistance = 20 Ω )

R = ρ l / A

If we increased the length of wire twice of its previous length then new length become 2l and area of cross section become half

$r \: = \frac{ρl}{a} \\ \\ r \: = \frac{ρ \times 2l}{ \frac{a}{2} } \\ \\ r \: = \frac{4 ρl}{a} \\ \\ i.e \:$

R = 4R

R = 80 Ω

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