. The masses of three copper wires are in the ratio

1:3:5 and their lengths are in the ratio 5:3:1 . The ratio of their resistance is

A: 15:1:125

B: 1:125:15

C: 125:1:15

D: 125:15:1

Explanation:

Resistance is given by

R = pl /A = PL²/V (A=V/L)

= PdL²/ m(V=m/d)

It is given that the three wires are of same material,

so density and resistivity will be same of all the wires.

So,

R∝ L²/ m

Now, let

M₁:M₂:M₃=1:3:5

L₁:L₂:L₃ =5:3:1

R₁:R₂:R₃= L²₁/m₁:L²₂/m₂:L²₃/m₃

=5²/1:3²/3:1²/5

=125:15:1

So, option (D) is correct.

Final Answer:

Hence, option (D) is correct. ( 125:15:1 )

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