Recent content by BlackMelon

Hi Dave Please refer to the current loop in the following link: http://bit.ly/3B5buxz The Ampere's Law and the Biot Savart Law mismatch in this case. The reason is that the magnetic field along the Amperian loop is not constant. Yet, we see from Hyperphysics site: bit.ly/4d7PAaj that if the...

Hi All, In the attachment, I have 3 scenarios in question. The first one is just a solenoid from http://hyperphysics.phy-astr.gsu.edu/. The second one is a hollow cuboid, which is infinitely long. I am using the same analogy as the solenoid. Would I be able to set the same Amperian loop? For...

Curl (V1) = V2 means that V1 is perpendicular to V2, right? From the Maxwell's Equation Curl(B) = u0J +u0e0(dE/dt) means B is perpendicular to the summation of u0J and u0e0E (since dE/dt has either the same or reversed direction of E) In my case, it is not the current that flips its polarity...

Hi there! Recently, I have been reading about polarization of a wire's insulator. First of all, I want to see a connection between the last Maxwell's Equation: $$\nabla\times\\B\ =\mu_0\ J\ +\mu_0\ \epsilon_0\ \frac{\partial E}{\partial t}$$ and the polarization. So I draw a simple cartoon...

Thank you all. Next time, I will make the problem easier to understand. Inductance range 10uH to 10mH Voltage = 12Vdc Current and period of time are < 3 A and 10 ms (may be) I have just got an idea. I will just apply the 12Vdc until the inductor reaches its steady state to measure the series...

Hi! Please refer to the word file. I am thinking of measuring inductance of an inductor by applying a DC voltage onto it. Then, calculate L = V/(di/dt). I wonder if the series resistance (R) of the voltage source plus of the inductor under test would cause much error. So, I derive the...

Thank you very much for the explanation :)

Hi there! I would like to know if the following simplification is correct or not: Let A be a function of x, y, and z $$\frac{\partial^2A}{\partial x^2}+\frac{\partial^2A}{\partial y^2}$$ $$=\ \frac{\partial^2A\partial y^2+\partial^2A\partial x^2}{\partial x^2\partial y^2}$$...

Adding more information to my previous comment, here is how I calculate the current density inside the wire using curl(H) = J

Oh well it's zero. That was the silly of me LOL. Thank you very much. By the way, I have analyzed the inside of the wire H = I*r/(2*pi*R^2) a_phi. where r is the radius from the center of the wire to the point of interest. R is the radius of the wire. And got the correct answer: J = curl (H) =...

Hi there! Please refer to the picture below. I would like to understand the equation Curl(H) = J, where H is the magnetic field intensity and J is the current density. So, I inspect a simple problem. There is a wire carrying current I in the z-axis direction. a_r, a_phi, and a_z are the unit...

Guys, I got the answer for the question I asked. The distribution of windings' positions are incorrect. (The way I analyzed the number of poles was correct and showed abnormality). Rather, the distribution should be done as the picture below. According to the right and rule (The thumb is the...

Well, I understand your point. You bring the phase W like I drew and then examine its number of poles (4 poles). However, when you input the 3 phase currents into the motor, the number of poles will not be 4x3. Rather, it will still be 4, considering the directions of all the currents in the...

(I have modified the picture a little bit for clarity) Hi there! I had a chat with my colleague. He believes that the 3-phase induction motor on the picture below has 2-poles. There are 12 slots. Each phase contain 2 coils. I have showed how the coils are connected for the phase W at the...

May I know which part of my expansion is confusing?