when u heat the metallic disk the hole in centre of will expand or close?

Question

its about THERMAL EXPANSION

Answer 1

The expansion takes place over the whole disk, so the hole would also get larger, but almost not enough to notice.

Answer 2

It will expand.

It's easier to first imagine a solid disc, i.e. one without a hole in it. Now imagine that you can balance this disc at its centre so that it is horizontal and you also draw a circle where the hole would be. You now start to heat the disc up, how will the drawn circle move with repect to the centre point? Well the metal is expanding, so any point on that circle must be moving away from the centre (our fixed point) and so the circle as a whole is getting bigger. Now replace the drawn circle with the hole and you see that the hole expands.

Of course we're assuming here that we aren't using some fancy metal that actually contracts when heated up (i.e. has a negative temperature coefficient)

This has practical uses. For example, suppose you want to make that disc into a wheel and fit it onto an axle. Well you start with an axle that is just a bit bigger than will fit into the hole on the disc, you then heat the disc up until the hole has expanded enough to put it onto the axle and you then let it cool back down. It makes an incredibly tight fit.

Answer 3

The hole gets bigger. To prove this:

1. When something expands all dimensions expand equally so the hole gets bigger. Think of 3x3 square grid made of metal marked into squares with the centre square missing. If you heat it all the squares get larger, but retain their shape - in this case it is easy to see the square hole in the middle is now larger. Once you have that in your head the ring thing becomes clear.

2. Do it by experiment if you heat up a ring with a hole just bigger than a bar, then thread it over, then cool the ring the ring closes tight onto the bar. This works and is used in industry when such a joining is required.

Answer 4

It expands because, other than ice, everything expands when heated. this means that the molecules along the inside of the disk would have to expand against each other, and since they can't expand into the center of the disk they have to push against each other. This increases the circumference of the inside of the disk (as well as the outside) and makes the hole expand.

Answer 5

It expands. To see this, consider the expansion in the circumferential direction of the matter just outside the hole. Since it does expand, the circumference increases, so it follows that the diameter increases also.

Answer 6

take a rod and heat. it elongates. bend it and make it a circle. heat. does the rod ( now circular shape) 'elongates'?? as the ends are not free can it elongate? i dont think so. now think about the circle as the metallic disc. as for the rod the cross section should also expand on heating. the inner side doesn't have the freedom to expand as does the outer side. so does it close? chance is for the hole to close a little. i dont think hole will expand. anybody knows it practically??

Answer 7

the hole sholud be closed,, coz when metal disk got heated,, its expand,, expand from all sides so its also expand towards hole,, gradullay closing it,, (but if the heat is to much,, then the disk is melt in liquid form) ok

Answer 8

Expand.

Answer 9

The hole will Expand..

Answer 10

The hole will grow smaller.