Question

16. In order to have a difference of 25 cm in their lengths at all temperature, lengths of

iron and copper rods at 0oC are

 

6 6 12 10 / , 18 10 / o o   of iron C of copper​

Answer 1

Answer:

answer : option (4) 60cm , 85 cm

let length of iron is x and length of copper is y

a/c to question,

x - y = 25 cm .......(1)

difference of their lengths is 25cm at all temperature.

x - y = x(1 + α_i∆T) - y(1 + α_c∆T)

⇒x - y = (x - y) + (xα_i∆T -yα_c∆T)

⇒x/y = α_c/α_i = {17 × 10^-6/°C}/{12 × 10^-6/°C}

⇒x/y = 17/12

⇒12x = 17y .........(2)

from equations (1) and (2) we get,

12x - 12y = 25 × 12

⇒17y - 12y = 25 × 12

⇒y = 60 cm and hence x = 85 cm