Question

A resistance wire made from German silver has a resistance of 4.25ohm. calculate the resistance of another wire made from same material such that it's length increased by 4 times and area of cross section decreases by 3 times.

Answer 1

Heya mate, Here is ur answer

resistance of first wire = 4.25 ohms.

We know that resistance = rho × l/a

where rho = resistivity of the material

l= length

a= area of cross section

When length is increased four times,

length becomes = 4 l

When area of cross section is decreased 3 times, so area of cross section becomes

a/3

So, new resistance
$= p \frac{4l}{\frac{a}{3} }$


$= p \frac{4l \times 3}{a}$

$= 12 \: p \frac{l}{a}$


$= 12 \times previous \: resistance$


$= 12 \times 4.25$


$= 51$


So, new resistance is 51 ohm

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@Laughterqueen

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Answer 2

..... hope it helps....