# Search results

1. ### 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...
2. ### 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...
3. ### 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...
4. ### 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...
5. ### 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...
6. ### 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 /...
7. ### 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...