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In the right figure, the top panel of graph shows the potential V as a function

ID: 1438623 • Letter: I

Question

In the right figure, the top panel of graph shows the potential V as a function of position x in three regions I, II, and III. Accordingly, four parallel plates, A through D, can be setup to realized the distribution of potential, as schematically drawn in the bottom panel of the figure. The unit of the distance is cm, and the unit of potential is V. The potential on plate A is The magnitude (i.e. absolute value) of the electric field in region II is A particle carries -12e charge (i.e. q = -1.92 x 10^-18 C) and is free to move in region III. Its initial velocity is zero at position x = 8 cm. When it leaves region III, how much is the kinetic energy of this particle in eV (electron-volt)?

Explanation / Answer

here,

from the graph ,

the potential at point A is

potential at A = 10 V

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for the region 2 ,

electric field in II = - change in potetnial/seperation

electric field in II = -(5 - 10)/(4 - 2)

electric field in II = 2.5 V/m

the electric field in II is 2.5 V/m

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change in potential for III , V = (-10 - 5)

V = -15 V

Now, kinetic energy of particles = -12 * e * (-15 V)

kinetic energy of particles = 180 eV

the kinetic energy of particles is 180 eV upon exiting III