If you work in units where c = 1 and h-bar = 1, all physical quantities can be described as having a dimension (unit) which is some power of the mass.
Mass, energy, and momentum have a dimension of mass (i.e. mass dimension = 1).
Length and time have a dimension of 1/mass (i.e...
Let me try.
I have three answers:
1) What makes you think that x and y should anticommute? - There is NO principle that says that for fermions all comutators are blindly replaced by anticommutators.
2) We have the same in Dirac fermions: x and y (which are usually denoted by u...
Maybe you are referring to the difficulty in explaining superconductivity in high-temperature superconductors by the BCS theory. However, this does not mean that BCS does not explain superconductivity in simple materials.
A professor who read my recently completed M. Sc. thesis commented that the thesis was good enough so that it was worth eliminating English mistakes from there. However, I can't do it better than I did, since I am not a native English speaker. So I am looking for someone who would be interested...
Paul Steinhardt from Princeton discusses this possibility in his papers about the cyclic model of the Universe. The papers are easy to understand, and you can find them on his website: http://feynman.princeton.edu/~steinh/
All materials are like this in some sence: the electrons are mobile, but the protons are not.
And in a diode the situation is uni-directional.
(Of course this has nothing to do with my original question).
Suppose there are n electrons with angular momentum quantum numbers L1, L2, L3, ..., Ln. The total angular momentum L of the atom can be any number between the minimum and the maximum of all non-negative combinations +/- L1 +/- L2 +/- L3 ... +/- Ln (in steps of 1). Same about combinations of the...
Your multi-plate capacitor is equivalent to n 2-plate capacitors connected in parallel.
The capacity of each 2-plate capacitor is given by
C = e0 e A / d
where e0 is a constant (epsilon-0), e is the dielectric constant of the paper (assuming that it fills all the volume between the...
"Calculate the energy of the electron measured from the conduction band edge."
Energy is defined up to an additive constant. The instruction above means that the energy of the conduction band edge should be considered as zero.
What is commonly the voltage in the high voltage lines used to transport electric energy over large distances? What is their resistance and inductance? What is the magnitude of the current flowing there?
This is not homework. This is a question from the sample Physics GRE exam (question 72), and the correct answer is (A).
When I saw this question I understood that it would be better if I knew something about voltage amplifiers before taking the exam. This is why I asked these questions...
After you measure the energy of the system once, it's state becomes the eigenstate of energy corresponding to the value you obtained. If you measure it again and again you will always get the same value.
Thank you very much!
I just wanted the order of magnitude such declination can be. If you say 5 degrees in UK, it is of the same order of magnitude as I got. I was surprised that it was so large. Before, I thought that I can really trust the compass. I knew that the magnetic and the real...
I am interested in the limit where the ratio of the densities of the heavy part and the light part is very large (infinite).
Probably the answer to this limiting case can be found without solving differential equations...
Great answer, Warren! Thank you! Now I know much more about the voltage amplifier. But somehow it still isn't enough. I need to find an answer to the following question:
In a voltage amplifier, which of the following is NOT usually a result of introducing negative feedback?
Two parallel thin metallic plates with a gap between them are used as a heat insulator. How does the heat flow rate through this device depend on the temperatures on its two sides in the following two cases?
Case 1: The gap is filled with air.
Case 2: There is a vacuum in the gap.
A string has two parts: one with a very high mass density (per unit length), and the other with a very low mass density. A wave with amplitude A moves from the dense part toward the light part. What will be the amplitude of the wave which is transmitted to the light part?
Could you please tell me what the inputs and the outputs of a VOLTAGE AMPLIFIER are?
Also what do these mean (in a voltage amplifier):
- voltage gain
- positive/negative feedback
Suppose there is a line of atoms X and Y. For atom Y, S = L = 0, but not for the atom X. The arrangement is like this:
In the following 2 cases, will the magnetic moment depend on whether the magnetic field is applied to the right or to the left? (The...
Here are the answers:
1. The new state is not stationary. The book is right. Actually, any time-dependent state can be written as a sum of stationary states.
2. Your result confirms my answer to question 1.
3. <H> is the average energy. Average is (E1+E2)/2, not E1 + E2...
For a particle with S = 1 in a state of Sz = 1, what are the probabilities to obtain the various values of the spin component if measured along a direction which makes an angle Q relative to the z-axis?
Is there a general method for an arbitrary value of S?