# Recent content by eJavier

1. ### How does a permanent magnet lift iron filings

Magnetic fields ain't like a hammer hitting a nail since the hammer does work. Magnetic fields are like the normal force on a ramp. It doesn't do any work since it's perpendicular to the displacement.
2. ### How does a permanent magnet lift iron filings

I said that a magnetic field can't SPEED UP electrons and I stand by that. It can deflect them of course. The fact is that the force that a magnetic field exerts on an electron is always perpendicular to the trajectory (same as a satellite in a circular trajectory in a central force field) so...
3. ### How does a permanent magnet lift iron filings

to krab: I finally found out what's the problem. The formulas you wrote for the energy and work are mechanical work. You still need to add the energy of the electric currents. If you do that then you'll get zero work. This is in one of Feynman's lectures, chapter 13 I think. I'm kind of busy...
4. ### Magnetic Monopole

The fact is that no magnetic monopoles have been ever found (like a point particle being the source of a magnetic field). If there were any magnetic monopole it would explain why is charge quantized. More info: http://budoe.bu.edu/~corth/monopole_faq.html [Broken]
5. ### How does a permanent magnet lift iron filings

Magnetic field don't work on any charged particle. This follows from the Lorentz force Law. If you want a proof just ask :D.
6. ### Introduction to Complex Analysis

I think you should be familiar with at least some Calculus before trying to get into Complex Analysis. I don't know if you are by the way, I ain't familiar with european education
7. ### Calculators Which calculator to get? Ti-89, or HP49G+?

In electrical engineering it's much more useful a TI 89 In civil/mechanical engineering I've heard that the HP rocks
8. ### Are certain integrals possible?

If by "integrate" you mean finding its anti derivative as a combinations of the functions we already know, then nope.
9. ### How was e computed?

calculate \lim_{n\to\infty} (1+\frac{1}{n})^n
10. ### How does a permanent magnet lift iron filings

Hi I have no problem with the above, except that as far as I know \vec{N}=\vec{m}\times\vec{B} comes from the Biot-Savart Law as shown by Jackson's book on page 150. Furthermore, a magnetic moment is defined for a current distribution J (Jackson p.146) What causes me trouble is that I'm...
11. ### Computerized wave display

If it's like using an oscilloscope, then you have to count how many divisions are in a single period, and with that you can calculte the freq. as well For the amplitude count how many divisions in the y axis does the waveform have
12. ### E/m question

The field E between the plates is \frac{1}{\epsilon_0} \sigma in SI units, that should give you a hint
13. ### Life as a graduate student

Thanks folks, keep'em coming
14. ### What's harder? Math, Physics or Engineering?

You're correct, furthermore, we Engineers and Mathematicians are focused on different things, even when studying the same topic. Generally speaking, the engineer ain't that interested in the theory, he just wants to know how to solve something, with the mathematicians is the other way around...
15. ### So what is it, in that case?

\int (1-x^2)^{1/2} = 1/2 ( x(1-x^2)^{1/2} + \arcsin x)