My physics teacher told me that one of the innacuracies of Bohr's Atomic Model is that the nucleus (positive) would attract the electron (negative) making it move as a spiral until it collapses with the nucleus. What I don't get is why the same thing doesn't happen with a planetary system. How...
I'm trying to understand the physical meaning of Maxwell's Equation, but I'm confused about what generates what. According to Gauss's Law, electric charge placed somewhere generates electric flux, whereas Gauss's Law for Magnetism says that charge itself doesn't generate magnetic field...
Could anyone help me solve the following problem?
Calculate the ratio of the conduction current density to the displacement current density of the electric field E = E_0 \cos(\omega t) in copper, to a frequence of f = 1 kHz. (Given: \epsilon_{Cu} = \epsilon_0, \rho_{Cu} = 2 \times 10^{-8}...
Thanks a lot for the help. I really think bulk getters are what I need, though I'm not familiar with the term. I've googled "bulk getters", but I didn't find a lot of information that could help me. Do you know any websites or books with information about bulk getters or where to buy them?
I am working on a project of a medical equipment which is supposed to absorb oxygen at a rate similar to the human body. I am looking for a process or a substance that would absorb about 200-300 ml of oxygen per minute. I can't use fire or anything that explodes. I was thinking about iron...
How do I calculate the magnetic field genereated by a very long metal plate with width w and current i flowing along the direction of the largest dimension? If I calculate the intesity of the magnetic field in a point with distance b from the border of the metal plate, I get:
B = \frac {\mu_0...
Does it appear to be right at least? I'm starting to think that my mistake was to consider the cylinder section having a uniform current distribution. Since the wires are isolated and don't "fit" perfectly in a cylinder (some gaps are left in between them), I may have used the wrong current in...
Could anyone please help me with the following problem?
A compact package contains n = 100 long straight wires, shaped like a cylinder with a radius of R = 0.500 cm. If each wire conducts i = 2.00 A, calculate the intensity and direction of the magnetic force per unit of length acting on a...
When using cartesian coordinates, I use the following expressions to calculate the cross product of the basis vectors:
i \times j = k
j \times k = i
k \times i = j
j \times i = -k
k \times j = -i
i \times k = -j
Can I do the same in polar coordinates? How could I write the cross...
I think I got it now:
\frac{\partial \arctan\frac{x}{y}}{\partial y}=\frac{-x}{y^2}\frac{1}{\frac{x^{2}}{y^{2}}+1}=-\frac{x}{x^{2}+y^{2}}
I just can't figure out what I did wrong in the other post.
But that's OK. Thanks a lot.
I'm going to try:
\frac \partial {\partial x} \arctan \left(\frac x y \right)
\tan \left(\arctan \left(\frac x y\right) \right) = \frac x y
Derivative with respect to x:
\sec^ 2 \left(\arctan \left(\frac x y\right) \right).\arctan' \left(\frac x y\right) . \frac 1 y = \frac 1 y...
OK, I figured it out myself.
Now I use:
\sec^2 \left(\arctan(x) \right) = \tan^2 \left(\arctan (x) \right) + 1 = x^2 + 1
What gives me:
\arctan '(x) = \frac 1 {x^2 + 1}
Maybe I can do something similar with the original derivatives. I'll give it a try.
Actually, I don't even remember how to find the derivative of \arctan(x) (the formulas you posted). I tried something like this:
\tan \left(\arctan(x) \right) = x
Differentiating in respect to x:
\sec ^2 \left(\arctan(x) \right).\arctan ' (x) = 1
\arctan '(x) = \frac 1 {\sec ^2...