# Search results

1. ### What are (a) the current density and (b) the electron drift speed?

Oh god...lol, I've been really stressed and all over the place lately, I feel dumb for missing that XD Thanks a lot rock, got it!
2. ### What are (a) the current density and (b) the electron drift speed?

Yea I....really just can't see another way out besides dong the following: J = n_e * e * v_d 588235 = 6*10^28 * 1.6*10^-19 * v_d v_d = 6.13*10^-5 m/s = 6.13*10^-11 um/s Where is this wrong...? /o_o\ 1.6*10^-19 is the charge of an electron...6*10^28 1/m^3 is the electron density, and 588235...
3. ### What are (a) the current density and (b) the electron drift speed?

Oh man lol, sorry about that! It's the electron density for aluminum: 6.0*10^28 1/m^3. But yea, like...I don't know. I've tried 6.13 * 10^-5, 6.13*10^-11, 6.13*10^-6, and 61.3*10^-6, with no luck. Should I try one of these again just in case, or what do you think it is?
4. ### What are (a) the current density and (b) the electron drift speed?

No, that wasn't it... It's really quite frustrating. This looks to be essentially the only part on the assignment I won't understand/get. Does anyone know what's going on with it?
5. ### What are (a) the current density and (b) the electron drift speed?

Hah, I should've known; thanks, I got the first part. The second part, however, I got wrong: I used J = n_e * e * v_d with the values: 588235 = 6*10^28 * 1.6*10^-19 * v_d and solved for v_d I got 6.13*10^-5 m/s and then converted to 6.13*10^-11 micrometers / second, and got it wrong...
6. ### What are (a) the current density and (b) the electron drift speed?

Homework Statement "The current in a 1.70mm x 1.70mm square aluminum wire is 1.70 A. What are (a) the current density [in MA/m^2] and (b) the electron drift speed [in micrometers/second]?" Homework Equations J = I/A The Attempt at a Solution I plugged in the values for current...
7. ### What is the potential difference across the capacitor?

I did - but I apparently suffered a flurry of math errors. I got it anyway :)
8. ### What is the potential difference across the capacitor?

Homework Statement "Two 2.1cm x 2.1cm plates that form a parallel-plate capacitor are charged to +- 0.705 nC. What is the potential difference across the capacitor if the spacing between the plates is 1.20mm? " Homework Equations C = Q/V C = epsilon * A/d The Attempt at a Solution I...
9. ### What is the electric potential at the point indicated with the dot in the figure?

Homework Statement What is the electric potential at the point indicated with the dot in the figure? http://img842.imageshack.us/i/29ex26.jpg/ Homework Equations E = V_c / d ? V = E*s? V = k * q / r ? The Attempt at a Solution I'm really rather confused by this problem...
10. ### Two point charges with electric potential energy?

Exactly, lol...I mean, I would think maybe if you cut the potential in half then solve for q then q1 and q2 would be equal? But that doesn't seem right at all... I'm a bit confused. How would I go about doing it?
11. ### Two point charges with electric potential energy?

Homework Statement "Two point charges 2.0cm apart have an electric potential energy -180 microJoules. The total charge is 31 nC. What are the two charges?" Homework Equations V= k * q / r The Attempt at a Solution I understand that V = -180 * 10^-6, k = 9*10^9, r = 0.02m, and the...
12. ### The potential difference necessary to accelerate an He+ ion ?

You're absolutely right :D Got it, ty!
13. ### The potential difference necessary to accelerate an He+ ion ?

The potential difference necessary to accelerate an He+ ion....? Homework Statement "What potential difference is needed to accelerate a He+ ion (charge +e, mass 4u) from rest to a speed of 1.2×10^6 m/s?" Homework Equations K_f + q*V_f = K_i + q*V_i The Attempt at a Solution I figure...
14. ### Two circular discs spaced apart from a parallel plate capacitor ?

D'oh! That was it! Hahah - thanks much, and sorry for the confusion :) You just allowed me to pass this assignment ^.^
15. ### Two circular discs spaced apart from a parallel plate capacitor ?

Homework Statement Two circular disks spaced 0.50 mm apart from a parallel-plate capacitor. Transferring 1.90 x 10^9 electrons from one disk to the other causes the electric field strength to be 1.90 x 10^5 N/C. What are the diameters of the disks (in cm)? Homework Equations E = Q /...
16. ### Strength and direction of an electric field at a particular point problem

Well I actually just think I might be on the right track for these parts at least...though honestly I'm really quite confused still, having not done anything like this in years (you'll see that from my work, I'm sure...). My work: <Note: I've labeled the charges as such: E1 is for the field...
17. ### Strength and direction of an electric field at a particular point problem

Hello all - this is my first time giving this forum a try. I've been using another site for a while but it's just too spotty and not enough folks there care to give decent responses, so here I am :) Homework Statement http://img684.imageshack.us/i/27p28.jpg/ What are the strength and...