Question

Three very large charged metal plates are arranged as shown. The radius of each plate is 4 meters, and each plate is w = 0.05 mm thick. The separation d1 is 8 mm, and the separation d2 is 3 mm. Each plate has a tiny hole in it, so it is possible for a small charged particle to pass through all the plates.

You are able to adjust the apparatus by varying the electric field in the region between location D and location F. You need to adjust this setting so that a fast moving electron moving to the right, entering at location A, will have lost exactly 5.2e-18 joules of kinetic energy by the time it reaches location G. Using a voltmeter, you find that the potential difference VC − VB= -14 volts.

Consider the system of (electron + plates). Neglecting the small amount of work done by the gravitational force on the electron, during this process (electron going from A to G):

ΔK + ΔU= _____ joules

What is the change in potential energy for the system during this process?
ΔU= _____ joules

VG − VA=_____ volts

VF − VD= _____ volts

What is the magnitude of the electric field in the region between location D and location F?
|E| = _____ V/m

Answer 1

The net energy is constant. The energy lost as kinetic energy is equal to energy gained as potential energy From the above equation, the change in potential energy for the system is, = 5.2x10-18 J The potential energy between the points G and A is AU AG 5.2x10-18 J 1.6x10-19 C -32.5 V The potential difference between F and D is --32.5 V-(14 V) 18.5 V The magnitude of the electric field is, 18.5 V 3 mm 6. 17 × 103 V/m