Question

90. If the radius of the wire of resistance R is made
n times, its mass remaining constant, then its
new resistance will be
(b) nºr
R.
R
(c)
(d)
n4
(a) n’R
22
01
The temperature officiel​

Answer 1

Answer:

Let's say the radius of the wire is r and it's length is L

It's volume will be V = rL

Now, radius is made n times, hence it will be nr

Because the mass remains the same, hence it's volume will also be constant.

Hence, V = nr x L/n ( Length should reduce by a factor 1/n to keep the volume constant )

R is proportional to L/A

L = L/n

A = pi* (nr)^2

R' = R/n^2

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A1 = (n^2)(r^2)pi

Volume=constant

(n^2)(r^2)pi L = (r^2)pi l

L= l/(n^2)

A= (r^2)pi [A1 = n^2A]

R1 = xl/[(n^2)(n^2)A]

R1 = R/(n^4)

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