Question

The copper wires whose masses are 8 gm and 12 gm have length in the ratio
3:4. Find the ratio of their resistances.
[ ]
A) 2:5
B) 4:5
C 25:16
D) 16:25
​

Answer 1

Answer:

c..............................

Answer 2

Answer:

Here, m

1

=8gm,m

2

=12gm.

And the ratio of there lengths is 3:4.

So, l

1

=3s,l

2

=4s, where s is also a proportionality constant.

Now the resistance of a wire is R=ρ

A

l

=ρ

V

l

2

=ρ

M

l

2

d

.

Using, density(d)=

volume(V)

mass(m)

. Or, R∝

M

l

2

.

∴R

1

∝

3s

8

2

∴R

1

∝

3s

64

∴R

2

∝

4s

12

2

∴R

2

∝

4s

144

Using it the ratio of their resistance is 27:32