A question about heating aluminium with a hole in it

In summary, the conversation discusses the question of what happens to the size of a hole in a plane aluminum plate when the plate is heated. The options of the hole expanding, getting smaller, or staying the same size are explored, with the conclusion that the hole will always get bigger due to the expansion of the material. The concept of the coefficient of expansion is also mentioned.
  • #1
fluidistic
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Hi PF,
I watched a video on youtube about a physics professor who asked some questions at the end of the video but didn't answer them. One really interested me.
If you have a plane aluminum plate with a very little hole say in its center and you heat the whole plate. What happens to the size of the hole?
1-It could expend as the plate would do. 2-It could get smaller because the walls of the hole would expend where the hole is. 3-Or it could be of the same size.
I thought it would stay more or less of the same size because of 1 and 2 combined.
But I asked a friend of mine (I find him really brilliant) and he told me it would expend because there's no point on the aluminum plate that would get compressed. I was amazed about how fast he answered to the question and I think he is right.
So I'm asking you in order to be sure of it! Thanks.
 
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  • #2
Hi fluidistic. This question actually comes up quite a bit in the real world. There are lots of instances where there's a hole in a part that gets hot and you need to know what happens to the size of that hole. The hole always gets bigger assuming the material expands. Think of it this way - all the molecules or atoms simply get farther apart.

To calculate the increase, just use the coefficent of expansion and multiply times any given dimension. So let's say the expansion coefficient results in a linear part increasing in length by 0.001" per inch. For a hole in a part, the diameter would similarly increase 0.001" per inch.
 
  • #3
The hole gets bigger. Just think about what'd happen if you just _drew_ a circle on the plate. It'd get bigger right? Or if you cut out a circular bit and heated it the same amount? It'd get bigger too, but it should still fit in the hole (since they're the same temperature?, right?
 
  • #4
Ok thanks to both! My friend was right. I understand better now.
 
  • #5
Of course, if we fix the edges of the plate, the hole will get smaller...

A further question that might be interesting to explore: what edge constraint would result in the hole not changing size or shape?
 

Related to A question about heating aluminium with a hole in it

What happens when you heat aluminium with a hole in it?

Heating aluminium with a hole in it can cause the hole to expand due to thermal expansion. This is because as the temperature of the aluminium increases, the molecules vibrate more and take up more space, causing the material to expand.

Will the hole in the aluminium close when heated?

No, the hole will not close when heated. As mentioned before, heating aluminium causes it to expand, not contract. The hole may appear smaller in comparison to the expanded material, but it will not close completely.

Can heating aluminium with a hole in it cause it to break?

It is possible for heating aluminium with a hole in it to cause it to break, especially if the hole is near the edges of the material. This is because the expanded material may put pressure on the hole, causing it to crack or break. It is important to carefully consider the placement of the hole when heating aluminium.

Does the size of the hole in the aluminium matter when heating it?

Yes, the size of the hole in the aluminium can affect the expansion and potential for breakage when heating it. A larger hole may cause more stress on the surrounding material, increasing the likelihood of breakage. It is important to consider the size and placement of the hole when heating aluminium.

Are there any safety precautions to take when heating aluminium with a hole in it?

Yes, it is important to take safety precautions when heating aluminium with a hole in it. Make sure to wear protective gear, such as gloves and eye protection, to avoid burns or injuries. It is also important to carefully monitor the temperature and avoid overheating the material, as this can increase the risk of breakage.

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