Topic 2 - Heat, Electricity and Magnetism

 

The Sciences:  Chapter 4, 5 and 6

 

1)  There is an old saying that lightning never strikes the same place twice.  Given what you know about electrical charge, is this statement likely to be true?  Why or why not?

 

Answer:  The old saying is false.  Some spots are more likely to concentrate charge and thus more likely be struck by lightning.  Pg. 101-102

 

2)  Why does the tile floor in a bathroom feel colder to your feet than a rug does even though both are at the same temperature?

 

Answer:  Look at pg 80 in the text.  This deals with conduction.  Both objects are the same temperature, but the tile floor is a good heat conductor as it moves heat rapidly away from the skin, which is warmer than air temperature.  The rug is a good heat insulator (poor heat conductor) in that it impedes the flow of heat and so feels comparatively warm. 

 

3)  Why do people wear light-colored clothing in summer and dark-colored clothing in winter?  Explain your answer.

 

Answer:  Dark colored dyes appear dark to our eyes because they are absorbing most of the colors/wavelengths of visible light.  They absorb the energy from these waves.  Light-colored dyes are reflecting most of the colors/wavelengths and thus absorbing less energy.  This will cause them to remain cooler. Pg. 135-136.

 

1. I am really not sure about this.  I don't understand the electrical charge info but I would think that the odds are unlikely that lightening would strike the same place twice, but taller buildings and trees are much more likely to be struck numerous times?  I really am not sure.

2.  I guess it would depend on the heat capacity of each object?  I guess I would say the tile absorbs heat, which feels cold on your feet, while the rug reflects the heat (like a blanket) back to your feet.  I am not sure about this is either.

3. My first thought is that light-colored clothing reflects more of the sun's heat, while dark-colored clothing absorbs more heat.  So in the winter you wear dark to absorb more heat and the summer for the opposite reason.

 

#1. In the same storm, I would think that lightning wouldn't be able to strike the same place twice because of the charge exchange.  In a thunderstorm, the ground is positively charged and the cloud is negatively charged making the ground and cloud electrically attracted to one another.  When lightning strikes, charges are exchanged making the cloud and ground (in that particular place) both either positively or negatively charged (balancing them out).  I think???  Of course, lightning can hit the same watertower twice during two separate storms on two different days...

#2.  This is what I would assume...A rug would be warmer feeling because "carpet" is an insulator that transports heat to the person stepping on it.  Tile would be colder because it is not an insulator, so it takes heat from the person stepping on it????

#3Light colored material (especially white) reflects light, making the person wearing the clothing cooler.  Dark colored material (especially black) attracts light, making the person wearing the clothing warmer.  I did a science fair project on this in 7th or 8th grade by shining a lamp on different colors of the same kind of material and measuring the temperature on the side of the material that the lamp was not on. Results: the lighter the color, the cooler you will be:).

 

1. I think that it could be true.  Objects touched with the same force,have the same electrical charge and therefore  they repel each other. Thats why I think that the statement could be true.

2. I think that the rug feels warmer because it has more heat energy than the tile floor does.  

3.   Light-colored clothing is worn in the summer and dark colors are worn in the winter because the darker colored clothing attracts and stores more radiation from the sun than light colored clothes. In the summer a person wants to be cooler so they wear light colors because they don't want to attract the heat from the sun where as in the winter people want to be warmer so they where dark colors so it attracts more sun light.

 

Q1=Well, I would have to disagree with this statement.  Lightning rods are things that are specifically designed to attract lightning so buildings aren't destroyed.  Electric charges are changed during thunderstorms and there is always a threat of lightning striking.  There is nothing stopping it from striking the same place twice.

Q2=A tile floor is a heat conductor.  It doesn't hold heat very well and it releases heat fast.  The rug on the other hand is what is called a heat insulator.  It impedes the flow of heat and therefore feels warmer to the touch.  This is same principle in the insulation of houses to keep heat inside the house.

Q3=Heat is attracted to dark colors.  Dark colors also keep heat in better.  That is why one would wear dark colors in the winter and light ones in the summer.  Light ones will not suck in heat like the dark ones do.

 

Q1=I would say this statement is not true. 1st of all our house was hit by lightening twice. Second from the reading in the book it states that Eclectrons and nucleus have an opposite electrical charge so there is an atractive force exsits between them. I take that to mean that the lightening is the electron and the object that it hits is the nucleus.  We should probably invest in a lightening rod.

Q2=Becuase the carpet store the heat longer then the tile does. The tile is a good heat conductor so it moves heat away from your feet while the carpet is a good heat insulator so it does just the opposite of the material that is the conductor.

Q3=Lighter colors reflet heat and darker colores absorb heat. The darker colors must work like the fiberglass insulation in the book. So then the darker color must disrupt air flow and prevent airflow and prevent heat transfer. The opposite must happen with the lighter colors to make this a true statement.

 

Q1=Lightning never strikes the same place twice?  Lightning can strike the same place twice---it is possible.  If the object is close to the source of the lightning in the relative vicinity of the source and close as in taller than the surrounding area, then there is a good possiblity that lightning will strike twice.  That's why Benjamin Franklin invented lightning rods to be placed on buildings, with lightning being attracted to higher structures, the lightning rods save homes from being struck directly, and more than once.  If lightning didn't strike in the same place more than once, there would be a greater chance of lightning striking people, animals, or building and natural infrastructure.

Q2=The rug is a form of insulation, being able to store heat, whereas the tile floor doesn't store heat in anywhere close to the capabilities that a rug can.  Just by a person walking or standing on the rug, heat is temporarily stored in the material.  The tile floor has no easy way to store heat, unless a source of heat is in direct contact with it which heats it.  Otherwise, the rug will feel warmer because it's fibers are more conducive to storing heat than a tile floor.

Q3=People wear light clothing in the summer and dark clothing in the winter for very good reasons.  Dark clothing attracts heat much easier than does the lighter clothing.  The darker materials draw in the heat from the sun light and store them, making people sweat or warm up very easily in the summer climate.  In winter, the same principle holds true, keeping the individual warmer in the cold climate than in the lighter clothing.

 

1. Electrical charge is an excess of electrical charges on an object. In the case of lightning striking the same place twice, I think it can. I'm not sure how to explain this, but the lightning could hit a piece of land and that would all be one object, but not necessarily the same spot. This is a hard question, but I do think this is possible. If I slide my feet across a carpeted floor and then go flip on the light switch, I get shocked. If I went and slid my feet across the carpet again and went to flip on the lights, I would get shocked again. I think this may show that lighting can strike in the same place twice.

2. The tile feels colder because it is a good heat conductor and it moves heat rapidly away from your skin that is warmer than air temperature. The rug would be a heat insulator. The rug slows down the flow of the heat which would make it feel warm.

3. Light colors feel cooler in the summer. Dark colors of clothing, such as black shirts, absorb more light, or energy, and therefore make a person feel warmer while wearing them in the summer. Lighter colors do not absorb as much heat and feel cooler on a person's body.

 

1. I think this statement could be true.  I think there is something that pulls the electrical charge to that spot and once it hit that spot the pull is not there anymore so it won't want to hit there again.

2. I think the rug aborbs heat where as the tile floor does not.  It's like water.  If you put water on the rug, the rug is going to soak it up, but if you put water on the floor, it will just stay until someone cleans it up or it evaporates.

3. Well people are not very cheery in the winter time because of the wheather.  It puts them more in a down mood, so they tend to wear darker clothing.  I mean look at the weather today.  And in the summer time you feel good and your in a good mood.  The sun is out and you more cheerful, so therefore you wear more brighter clothes.

 

Q1=This statement is very false.  the truth is simply that lightnight will strike wherever there is an electrical condctor.  it can strike in the same place more than once, or around the same place more than once.  its as simple as that.  so stay away from conductors of electricity!!!  :)

Q2=hmmm....this is a good one, i would guess that it is because the rug has more kinetic energy because it has more molecules.  maybe?  or, if a rug has more thermal energy, than it is capable of keeping heat in longer and therefor will make it seem warmer to the touch. also, you have more friction when you walk on carpet so that can produce heat and make it seem warmer. i dont know though, these are just guesses!!!

Q3=so that they stay cooler or warmer.  since dark colors attract heat people usually wear darker colors so that they stay warmer.  lighter colors dont attract heat as much as dark colors so if they want to stay cooler in the summer they will opt for lighter colors!  i guess, maybe there is some scientific explanation, but that works good enough for me!!! :)

 

1. I don't think this saying is true.  The ground is positively charged and storm clouds are negatively charged.  There is the same potential for lightning striking somewhere that it has struck before as there is to strike somewhere it has never struck.

2. The tile floor feels colder than the rug even though they are both at the same temperature because of heat transfer.  Temperature and heat are not defined as the same thing, even though many people mistakenly interchange them.  The rug conducts heat better than the tile.

3.   People wear the colors they wear during certain seasons to maintain body heat more efficiently.  Light-colored clothes reflect the sunlight therefore keeping the body cooler.  On the other hand, dark-colored clothing is worn in the winter because it absorbs the sun's heat and keeps the body warmer.

 

Q1=Wind and rain disrupt electrons in clouds during a storm.  The positive charges on the ground attract to the negative charges in the clouds causing lightning.  There is a definite possibility that lightning COULD strike the same place twice.  Trees and poles, all have positive energy flowing through at all times from the ground.  There is a chance that something could be stuck a second time.

Q2=The difference in temperature is due to specific heat capacity.  Certain materials have certan abilities to absorb heat energy.  The rug can probably absorb more heat than the tile floor.  That is simply how each of the materials absorb.  Some materials can't take in heat as fast as others.

Q3=The reasoning for people wearing light-colored clothing in summer and dark-colored clothing in winter is because of the fact that the suns ultraviolet rays come from above and the darker color of clothing absorbs heat much quicker than lighter articles of clothing.  With the darker clothing people will begin to sweat in reaction to the intense amount of heat through the clothing.  So, people wear the lighter clothes so that the heat doesn't absorb into the material as quickly, causing the person to sweat.

 

Q1=This statement is more than likely not true.  Lightning is caused by the attraction of positive charges on the ground to the negative charges in the cloud.  Therefore there is nothing that would affect whether it strikes the same place twice.  There will still be positive charges in that place on the ground where lighning struck before that would allow lighning to strike there again.

Q2=A tile floor feels colder than a rug does on your bare feet because of the heat capacity of them both.  The carpet or the rug is able to absorb the heat better than the tile floor.  It is like when water heats up very quickly, but a metal pan is able to heat up more quickly.  That is why the tile floor feels colder to your bare feet than a rug does even though they are the same temperature.

Q3=People wear light colors in the summer and dark colors in the winter because the dark colors attract heat more than light colors do.  This is because of the size of the wavelengths of the light.  Also because of the size of the wavelengths in the color of the clothes.  Like light and dark colors.