Recent content by null void

Sorry, I don't quite get you. I have searched around about that differential form, I am not sure what should i find with it. Q = \int\int D \cdot ds = \int\int\int \rho_v dv The Q is given in the question as a constant, D can be derived out by Coulomb's law. The answer for the question is V =...

Homework Statement - A point charge is placed at the origin of the medium. - The relative permittivity of the medium, \varepsilon_r = a / r, a is a constant, r is the radius from origin to any point around the charge. - Objective of this question is to find the expression for voltage.at any...

I think I get the things I want here, thank a bunch guys.

Sorry, I just notice there are some naming convention problem in my equations, A is a scalar, bacause \nabla can't multiply with a scalar (\nabla A \cdot\nabla)\vec B Now I know that the del is not commutative, but I want to conform if this is the right way to evaluate that expression, i have...

from what i see in the wiki page on "Del", i think the right operation is this one

so for the right side, it is something like this: \begin{align}(\nabla\vec A\cdot\nabla)\vec B &= (\frac{dA_x}{dx}\frac{d}{dx}+\frac{dA_y}{dy}\frac{d}{dy}+\frac{dA_z}{dz}\frac{d}{dz})\vec B\\ &= <(\frac{dA_x}{dx}\frac{d}{dx}+\frac{dA_y}{dy}\frac{d}{dy}+\frac{dA_z}{dz}\frac{d}{dz})...

Homework Statement Is there any difference between these 2 terms, if yes how are they different? \begin{align}(\nabla\cdot\nabla\vec A)\vec B &= (\nabla\vec A\cdot\nabla)\vec B\end{align} Homework Equations From what i know about dot product, it is commutative, so does this property apply here?

it is sin(x^2), i will make it clear next time

Oh yeah, what a silly mistake, thanks.

Homework Statement \oint_C{(x^2 + 2y + sin x^2)dx + (x + y + cos y^2)dy} the contour C formed by 3 curves: C(x,y) = \begin{cases}x=0, \quad from (0,0) to (0,5)\\y = 5 - x^2,\quad from(0,5) to (2,1) \\ 4y = x^2, \quad from(2,1) to (0,0)\end{cases} and the Stoke Theorem: \oint_C \vec F \...

Sorry for late reply, I think everything is fine now. Thanks you very much Simon, for guiding me to get the right equation.

Imagine that the curve revolve around the z-axis, and you can divide this volume into as many cylinders as u like to approximate this volume, volume of cylinder, V_{cylinder} = \pi r^2l but in this case, the r = y, l = dz thus, your small cylinder volume, dV dV = \pi y^2 dz by integrating...

http://www.ld-didactic.de/literatur/hb/e/p1/p1451_e.pdf I think my lecturer take the the source from this link, it look almost 100% same

r is the distance of the point-like mass to the center of axis and the L_{rod} is the length of the rode. The point like mass can be moved closer to the center, so the r can be change, but the L_{rod} always fixed at a length.

yeah the Torque and the period symbol almost look the same too... In my lab manual, the period calculation is: T^2 = \frac{8m\pi^2r^2}{D} + T^2_0 where the T_0 is the period of oscillation when the mass is removed from the rod. And the D is stated in my manual that it is the restoring torque...