Recent content by Juan Pablo

The force on a wire in magnetic field B is given by \vec{F_B} = I \vect L \times \vect B where L is a vector that points in the direction of the current and magnitude the length of the wire. So, \vec{L} = 0.29k \vec B = -2.04i-0.968j-0.328k Compute the cross product using a determinant.

Yes, solve the linear system of equations.

You're calculating the force not the charge. The force q1-q3 is: F = k_e \frac{q_1 q_3}{r^2} The force q1-q2 similarly. F = k_e \frac{q_1 q_2}{r^2} You can find the angle in q1 corner using the tangent function. Now sum them like vectors and you're done.

Homework Statement The circuit http://imgur.com/WSd2L. I'm asked to find the current and voltage on the capacitor using diff. eqns. It says that I can assume that the capacitor doesn't have charge at the beginning for the charging circuit and the capacitor in the only source of voltage for...

How kind! That was really useful collinsmark. Thanks a lot!

Yes, but I'm trying to analyze more complex circuits using Kirchhoff's laws. The first step on my book is assigning the direction of currents arbitrarly. However, I'm not sure how many different currents should I put. Thanks.

No specific circuit here, just a general question. Is there a general answer?

I understand pretty much everything related to this, except how many currents should I put when arbitrarly putting them. The number of resistors? The number of wires? The number of loops? I'm seriously lost here, thanks!

Yes, but I don't know if the fact that there are electrical and drag forces changes anything. According to Wikipedia the apparent weight equation is: W = \frac{4}{3} \pi r^3 g(\rho - \rho_{air})

What's the direction of the buoyant force? I'm trying to find the equation for the charge on the Millikan oil drop experiment. It requires two equilibrium equations but I'm not sure which sign should the buoyant force have. My internet searches neither my book have been able to answer this...

Apparently I misremembered. Another question, doesn't the electric field varies with distance? How is it possible to take it outside the integral?

That's pretty much what I was asking. Thanks a lot!. But isn't \vec{E} \cdot d\vec{A} an abuse of notation for the flux?

I've seen on most books and in class that Gauss's law is usually stated like \oint \vec{E} \cdot d\vec{A} = \frac{q_{en}}{\epsilon_0} Shouldn't the integral be a surface integral rather than a line integral? I've seen times in problem resolution where they evaluate the integral as a...

Thanks!

Homework Statement Find the work done a charge "q" of mass "m" by an electric field of magnitude "E" when it's moved a distance "d" 2. The attempt at a solution W = \int_A^B F_e \cdot dr = F_e \int_A^B dr = F_e d = qEd I used the Lorentz force equation for electrostatics at the...