Thermal coefficients of expansion

[Brian13]

Homework Statement

A brass rod (linear expansion coef 19*10-6/°C) has a radius of 8139 cm and a copper (linear expansion coef 17*10-6/°C) sheet has a hole or radius 8139+8.86cm. What temperature change (K) is required to close the gap?

Homework Equations

ΔL/Lo = αΔT?

The Attempt at a Solution

I'm not even sure if the equation is right, so I'm really confused. Thanks for the help!

 

[SteamKing]

Homework Statement

A brass rod (linear expansion coef 19*10-6/°C) has a radius of 8139 cm and a copper (linear expansion coef 17*10-6/°C) sheet has a hole or radius 8139+8.86cm. What temperature change (K) is required to close the gap?

Homework Equations

ΔL/Lo = αΔT?

The Attempt at a Solution

I'm not even sure if the equation is right, so I'm really confused. Thanks for the help!

That's some rod, if it has a diameter of over 16 meters!

Are you certain these are the dimensions for this problem?

 

[Brian13]

I'm positive!

 

[Chestermiller]

The equation is not correct. It should be:
$$L=L_0(1+\alpha \Delta T)$$So, if the temperature rises ΔT, in terms of #\Delta T#, what it the new radius of the rod? What is the new radius of the hole in the sheet?

 

[Brian13]

I'm not entirely sure. I don't really understand the formula, so I'm having a hard time really wrapping my mind around it. I don't know what the L represents.

 

[Chestermiller]

I'm not entirely sure. I don't really understand the formula, so I'm having a hard time really wrapping my mind around it. I don't know what the L represents.

Please say in words your understanding of the concept of thermal expansion.

Chet