Recent content by Michael_McGovern

  1. M

    Electric and magnetic constants are tensors

    That's intersesting Hurkyl. That is a much better definition of the tensor than the one I learned. I was trying to learn this stuff on my own and I got one book that was more physics-oriented and one that was more pure math. They both defined tensors in terms of the way their components...
  2. M

    Understand Isotropic Tensors for Physics

    Very helpful. Thank you!
  3. M

    Understanding Snell's Law & Total Internal Reflection - Explained

    Snell's law is definitely the way to go on this one. What went wrong when you tried to use it? Snell's law can be written as: \frac{n_2}{n_1}=\frac{\sin\theta_1}{\sin\theta_2} Theta 1 is the angle the ray entering makes with the vertical and is given as 37°. n1 is probably that of air which...
  4. M

    I Need Clarification on Ampacity, I Think (?)

    Oh, .1ohms! Didn't see the decimal place. That was stupid!
  5. M

    Why is Clapeyron Equation Positive for Most Materials?

    I'm not sure exactly what you mean. The equation says, for a phase transition: \frac{dP}{dT}=\frac{\Delta H}{T\Delta V} I think you're talking about dP/dT, but correct me if I'm wrong. Suppose you have a liquid that is being converted into a gas. This process is endothermic so \Delta H>0 and...
  6. M

    Not sure this is the right thread for this?

    It seems no one's really sure what to think. Look at https://www.physicsforums.com/showthread.php?p=877752#post877752 I'm skeptical, but apparently a lot of people are taking this seriously.
  7. M

    What Are You Studying This Spring?

    Next semester I'll be taking: Physical Chemistry II Boundry Value Problems Chemical Process Simulation Advanced Calculus I Heat Transfer Chemical Reaction Engineering Macroeconomics I hope that's what I'm taking anyway. There is a scheduling conflict between calc and BVP's, but I think the...
  8. M

    Formulea in Heat and Thermodynamics

    Actually you can't do this. Q is not a state function. Imagine you had a container that was thermally isolated from the surroundings so that Q=0. A chemical reation could still go on that would raise the temperature of the system. You can't always write that dQ=TdS. Remember that the...
  9. M

    What is the mass of the helium present - Thermodynamics

    The expression for the work done by the gas is: dW=PdV Since there is constan pressure we can write: V=\frac{nRT}{P} dV=\frac{nR}{P}dT So dW=nRdT and [/tex]W=\int_{T_1}^{T_2}nRdT[/tex] Do the integral, use the molar mass of He to convert the # of moles of He to the mass, and then solve for the...
  10. M

    Formulea in Heat and Thermodynamics

    I didn't notice that you switched between dV and dT- sorry that was my mistake. These are just formulas. For an ideal monatomic gas: c_v=\frac{3}{2}R; c_p=\frac{5}{2}R For an ideal diatomic gas: c_v=\frac{5}{2}R; c_p=\frac{7}{2}R
  11. M

    Electric and magnetic constants are tensors

    No, that is not right. The dot product is not a tensor, nor is the result of a dot product a (0,2) tensor-it is a (0,0) tensor a.k.a. scalar. You know that we can take several numbers and form a vector. Simmiliarly we can take N vectors of length N and produce an N by N matrix. One way we...
  12. M

    Formulea in Heat and Thermodynamics

    That looks fine, but remember you're solving for delta U, which equals Q, not Q itself. ================================================ That seems right. Since you are dealing with argon, which is a monatomic gas that behves close to idealy, they may want you to assume c_v=3/2R. For a...
  13. M

    Room Full of Hydrogen: Fusion or Entropy?

    It is not a question that can be answered by thermodynamics alone. It is like asking - suppose you have a gas contained on one side of a container by a wall, will the gas eventually expand to the other side of the wall? Clearly the entropy would increase if the gas were to expand so this...
  14. M

    Understand Isotropic Tensors for Physics

    Hello everyone, this seems like a great forum here with a lot of knowlegable people and I was hoping someone could help me out with this question. I'm an engineering student and I've recently decided to switch into physics. Now I'm trying to catch up on the math I'm going to need, so I'm...
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