a) Determine and express in unit vector notation the electric force that acts on

Question

a) Determine and express in unit vector notation the electric force that acts on each end of the molecule. Determine the net electric force that acts on the molecule as a whole and express this vector in unit vector notation. Determine the magnitude of the net force )ctorw doesthe direction of the dlectro field ector compare to the direction b) How does the direction of the electric field vector compare to the direction of the net force? Briefly explain how you know. c) What would be the net force on the molecule if the field were uniform and described everywhere around the molecule by the vector given. Explain/show how you know d) Water is a polar molecule, and in class it was shown that both the PVC and plexiglass pipes (charged) will bend a stream of water. (Here's a youtube reference for the same thing: https://www.youtube.com/watch?v VhWQ-rILYXY). Based on the analysis you've just carried out, how could this experiment be used to distinguish a uniform electric field from a nonuniform field? Explain how you know. 4) In the device below a 500 V difference of potential is maintained between two conducting surfaces: one is roughly a hemisphere and the other a flat plate. The space between the conductors is a vacuum and the electric field in this space is non uniform Several equipotential surfaces are shown. An electron crosses the 300 V equipotential surface heading in the general direction of the metal plate with a speed of 145 x 107 m/s. 50 V 100 V 200 V 300 V election 500 V a) Determine the electron's kinetic energy as it crosses the 300 V surface. How muclh kinetic energy will the particle have when it reaches the 100 V surface? Also determine its speed at this point. b) How much kinetic energy will the particle have as it reaches the metal plate (assuming it does)? c) Does the electric field (generally) point in the direction of the flat plate or the hemisphere? How can you tell? Discuss.

Explanation / Answer

a) initial speed ,u = 1.45 *10^7 m/s

as the electron is moving towards the 100 V plate , it's kinetic energy will change into potential energy

kinetic energy at 300 V = 0.50 * 9.11 * 10^-31 * (1.45 *10^7)^2

kinetic energy at 300 V = 9.58 *10^-17 J

Now, for kinetic energy at 100 V

kinetic energy at 100 V = kinetic energy at 300 V - increase in potential energy

kinetic energy at 100 V = 9.58 *10^-17 -1.602 *10^-19 * (200)

kinetic energy at 100 V = 6.37 *10^-17 J

for the speed at 100 V
0.50 * 9.11 * 10^-31 * (v)^2 = 6.37 *10^-17

solving for v

v = 1.18 *10^7 m/s

speed of electron at 100 V is 1.18 *10^7 m/s

b)

at the metal plate

as the electron is moving towards metal plate , it's kinetic energy will change into potential energy

kinetic energy at metal plate = 9.58 *10^-17 -1.602 *10^-19 * (300)

kinetic energy atmetal plate= 4.77 *10^-17 J

c) as the electric field points in the direction of decreasing potential

the electric field points in the direction of flat plate

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