Question

a copper wire has a resistance of 6 ohm another coper wire of the same mass as the first one is double in length of the fist.find the resistance of the second wire​

Answer 1

Given:

Resistance of first wire = 0.6Ω

Length of second wire = 2(Length of first wire)

Note:

We know that when length of wire is doubled , the area is halved.

So,

Area of Second wire = Area of first wire / 2 = 0.5 Area of first wire

Computation:

Resistance of first wire = 0.6Ω = p(Length of first wire) / Area of first wire

Resistance of second wire = p(Length of Second wire) / Area of Second wire

Resistance of second wire = p × 2(Length of first wire) / 0.5 Area of first wire

Resistance of second wire = 4 × p(Length of first wire) / Area of first wire

∵ [0.6Ω = p(Length of first wire) / Area of first wire]

Resistance of second wire = 4 × 0.6Ω

Resistance of second wire = 2.4Ω