Question

A wire of length 1m has resistance 2ohm . hwat is the resistance of a second wire , hwose resistance is doubled of the first ,if the length of the wire is 3m and diameter is doubled of the first

Answer 1

Explanation:

ANSWER

Given that,

Length of the wire l

1

=2m

Length of the wire l

2

=1m

Radii of the wire r

1

=1mm

Radii of the wire r

2

=2mm

We know that,

R=

A

ρl

Now, the specific resistances for both wires

R

1

=

A

1

ρ

1

l

1

R

2

=

A

2

ρ

2

l

2

As material is same of both wires

So, R∝

A

l

Where, A=πr

2

Now, the ratio of specific resistance is

R

2

R

1

=

ρl

2

×A

1

ρl

1

×A

2

R

2

R

1

=

2×r

1

2

1×r

2

2

R

2

R

1

=

2×1

1×4

R

2

R

1

=

1

2

Hence, the ratio of specific resistance is 2:1

Hope it helps