Question

The diameter of a wire is reduced to one fifth of its original value by stretching it. If its initial resistance is R,
what would be its resistance after reduction of the diameter?

A)R/625
B) 625R
C) 25R
D)R/25​

Answer 1

Answer:

option B

Explanation:

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Physics

Current Electricity

Electrical Resistance & Resistivity

The diameter of a wire is r...

PHYSICS

The diameter of a wire is reduced to one-fifth of its original value by stretching it. It its initial resistance is R, what would be its resistance after reduction of the diameter?

MEDIUM

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ANSWER

Initial volume= Final volume

A

1

L

1

=A

2

L

2

πr

1

2

l

1

=πr

2

2

l

2

r

2

2

r

1

2

=

l

1

l

2

R

2

R

1

=

A

1

ρl

1

×

ρl

2

A

2

R

2

R

1

=

l

2

l

1

×

πr

2

2

πr

1

2

⇒

R

2

R

1

=(

r

1

r

2

)

4

D

2

=

5

D

1

r

2

=

5

r

1

R

2

R

1

=

625

1