1.

A wire of length l and resistance R is stretched to get the radius of croos -section halved . what is the new resistance of the wire after streching ?

Answer»

Answer:

Answer

Correct option is

A

16R

Let length & cross sectional AREA of wire be ℓ & a respectively. ρ be the specific resistance, then

R=ρ

a

If radius BECOMES half, area becomes

4

1

th or cross sectional area after the stretch =

4

a

. Let its length increases to ℓ

. Since volume remains the same in the process,

ℓa=ℓ

×

4

a

⇒ℓ

=4ℓ

Let R' be the resistance of stretched wire,

R

a/4

4ℓ

=16×ρ

a

=16R

Explanation:

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