Recent content by Brennen berkley

Ok, with those assumptions I get 110,000 m/s, which is 9 orders of magnitude higher than the drift velocity. Thanks

Homework Statement How many orders of magnitude smaller is the average drift velocity of a hole than the RMS thermal velocity of an electron moving in free space? (Use the law of equipartition to find the RMS thermal velocity of a free electron.) This is the last part of the problem, I have...

I think you would actually do the calculation using R1 because it's losing energy, but shouldn't the energy gained by the second sphere equal the energy lost by the first sphere? I don't understand which capacitance to use when calculating the work. It seems like the capacitance should be a...

Using that equation, the work would be W = Q22/8πεoR2 = 1.248*1012 = 1.25 x 10-6 J. Is that right?

Oh, ok I found this equation for the self capacitance of a sphere The first few pages I looked at had other things that weren't useful.

I just don't understand how to figure out the capacitance, because it depends on the distance between the plates or whatever shape the capacitor is on. Voltage also depends on distance. Since the charge is traveling through a wire, distance doesn't have any affect on the problem (correct me if...

To be a capacitor there just has to be a charge difference between the two objects (voltage), but I'm not sure how to calculate the potential energy, that's the problem.

Homework Statement Consider two metal spheres, sphere 1 having radius R1 = 20 cm, and sphere 2 having a radius R2 = 10 cm. The two are rather close to one another, separated by a center-to-center distance of only 80 cm. Suppose now that they are connected to each other by a thin wire that is...

Homework Statement A capacitor is constructed of two long concentric metal cylinders, each having length of 1.0 meters. The inner cylinder has a radius R1 = 1.0 cm, and the outer cylinder has a radius R2 = 1.25 cm. The hollow space between the two cylinders is filled with nylon having a...

I see how to do it know, it's pretty simple, thanks.

Ok I'm still stuck. I used σ = q/πR2 and did the binomial expansion and got this: EDIT: that should be R2/2x2

Yes, I meant if x is much larger than R then √(R2/x2 + 1) goes to 0 (hopefully I said it right that time). I haven't done binomial expansions, for a while so I'll review those, thanks.

Homework Statement Take the expression 21.11 (pictured below, specifically the bottom one) for the electric field above the center of a uniformly charged disk with radius R and surface charge density σ, and show that when one is very far from the disk, the field decreases with the same square...

Using the new equation I got 1.44 x 10-16 W for the energy and 415,277 m/s for the velocity.

Thanks for clarifying. In class we have only covered the material through chapter 21, and all the electric potential stuff is in 23, so I haven't read about it very in-depth yet. I'm not sure why it's on our homework. Anyway, I think I understand what I need to do now. Potential Energy U = qV...