Monday, 28 July 2014

Physic Blog 24


My Personal Answer is when we enter an air conditioned room after work on a hot day, our body temperature is higher than the surrounding air, the molecules on our hand will be moving faster than the molecules in the room and when the molecules comes into contact, thermal energy is transfered from a higher temperature to a lower temperature molecules thus our body molecules loses thermal energy for it is transferred to the surrounding molecules and because the difference in temperature is big we will not feel cool but cold instead.


My Personal Answer is when we come out of a swimming pool, droplets of water are still on the surface of our skin due to our hair and other things and since it is a hot day, the water droplets on the surface of our skin will gain thermal energy much faster than usual from our skin's molecules and surrounding molecules and will evaporate and when they evaporate we lose thermal energy and since it is a hot day the process is much more faster thus speed up the process even more.  Thus with this sudden rapid loss of thermal energy, it causes us to shiver.

I learnt that heat is thermal energy and that temperature is the amount of thermal energy present in something and when they have high thermal energy, molecules move faster. I also learnt that metals have free electrons but non-metals don't. I also learnt how to draw the scales for different thermometers and also what is conduction.

  The tiles is a better conductor of heat than the parquet thus we feel warm on the parquet and cold on the tiles.

  We need to made an assumption that the surrounding air did not affect the temperature of the hot and cold water thus My answer is both the water will reach the same temperature at the same time. But the two lines will be slightly curved inwards. This is because as they gain and loss heat the gap between the temperature of both the water and the room temperature is decreasing and the bigger the gap the faster the transfer of thermal energy thus the line will not be steep like the beginning. 

 
My answer is that we need to take the ring and heat it up. Although when things expand, it expand in all directions, which would mean that the inner side of the ring will move inward, the outer side of the ring move out wards and the ring will also get longer in terms of the middle line's circumference. But when heated the molecules move faster and more collisions thus the molecules will want to have a bigger gap with the other molecules but when the inner side of the ring move inwards the molecules will be closer with one another due to the decrease in diameter with the same number of molecules, only can vibrate in its fixed positions thus the pressure will be high and there will also be resistance of the molecules and the ring might break thus it is the easiest to move out wards thus the diameter will increase both inner and other. Same for cooling of the ring.

What I learnt this week is the wider the temperature difference, the faster the transfer of thermal energy. I also learnt that when answering, we need to answer the question and not saying everything.


My answer is it bend because it is made up of two different metals with different rates of expansion. The metal with higher thermal expansion coefficient than the other expands more than the other but since the are fused together it cannot be apart from the other metal thus to expand it bend and also forces the other metal to bend with it. It straightens because there is a sudden drop  in temperature and their length is linear to its temperature thus when cooled it will the revert back to its original length.
This week I have learnt about different thermal expansion and how land and sea breezes are formed and how convection works.



Group Answer and Discussion is on Youtube: http://m.youtube.com/watch?v=i66XZQz5VwM
My answer is since the liquid in the container is transparent, we can assume that the effect of the liquid on the two other colored liquid is reduced. From the picture above it can be seen that as time goes on, the green and the red liquid mixed together. I think that this happens because of diffusion as the red and green particles for the green and red liquid will diffuse into the transparent liquid and then the green particles in to the red liquid and the red particles in to the green. The diffusion rate is slow because there is a difference in density between the two liquid and the transparent liquid thus they did not mix together as the transparent liquid is between the two liquid.

This week I learn that white colour is poor absorber and emmitor of radiation which black is just the opposite.