Question

A thick wire of resistance 5 ohm is drawn into a thinner wire of 3 times the length of the thick wire find its new resistance ​

Answer 1

Answer:

Since, volume is constant, i.e.,

πr

1

2

l

1

=πr

2

2

l

2

⇒(

r

2

r

1

)

2

=(

l

1

l

2

)=(

l

3l

)=3

Now,

R

2

R

1

=

ρ

A

2

l

2

ρ

A

1

l

1

=

r

2

2

l

2

r

l

2

l

1

=

l

2

l

1

×

r

1

2

r

2

2

⇒

R

2

R

1

=

3

1

×

3

1

⇒R

2

=9R

1

=9×5=45Ω