Actual PS questions from August Administration

[viagraguru]

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Question 1: Using the equation G=H - TS, when the Temperature is changed, what can be directly measured:

a)Enthalpy b)Entropy and Enthalpy c)Entropy d)enthalpy and free energy *my answer "c" cause only S is directly related to T.


*From EM passage
Question 2: When the voltage in a telephone cable is increased from 1V to 100V, what results: a) The magnetic field decreases B) Less heat is lost due to radiation c) The electric field decreases d) i wish i remember *my answer "B" cuz the current travels faster when voltage is incrased, so less heat can be lost due to radiation.

What do you all think?

 

[Trek]

Trek thinks it's time to move on already...

 

[SeeGulz]

Hmmm, my best guesses would be:

1) a.
2) d.

Too tired to give the rationales behind my choices, and I am probably wrong anywho. Good luck on your scores, though. I took the August test too, and I hope that I never have to take that bastard again 🙂

 

[bentz]

1) C
2) D

I do agree with your answer for the fist question. Entropy does increase as temperature increase. For example water molecule become more random at higher temperature than at room temperature. Thus I would pick your answer choice. However, I don't agree with your thinking for the second question. As the voltage increases from 1V to 100V in the phone line, more friction will be created on the wall of the phone. I am assuming the diameter of the line remain constant. As the friction forces increase within the phone line due to higher number of ions' movement, more heat will be formed or converted from one form to another one (I know heat can't be created or destroyed) inside the phone line. For instance, as potential energy increases, kenetic energy decrease and vice versa Then heat will flow from higher concentration to a lower concentration of heat. In order words, more radiation would be formed because it is the only mode for heat escape the phone line. None of the answer choices is correct. According to this formula V=IR. As voltage increases, the current increases as well. As the current increases more magnetic field will be formed. From the radiation explantion, you can also see The electric field will also be increased. I hope the was choice D. That is how I would think about it. Any refutable explanations anyone?