[1.] If it takes +1.6 x 10-5 J to move a positively charged particle between two

Question

[1.] If it takes +1.6 x 10-5 J to move a positively charged particle between two charged parallel plates,(A) What is the charge on the particle if the plates are connected to a 6.0-V battery? (B.) Was it moved from the negative to the positive plate or from the positive to the negative plate? (C.) What are the magnitude and direction of the electric field between the two charged parallel plates if the plates are separated by 4.0mm? [2.] An electron is accelerated by a uniform electric field (1000V/m) pointing vertically upward. Use Newtons laws to determine the electrons velocity after it moves .10cm from rest. [3.] How much work is required to completely separate two charges (each -1.4) and leave them at rest if they were initially 8.0 mm apart?

Explanation / Answer

PE=VQ

1.6*10^-5 J= Q*(6)

Q=2.7*10^-6 C

(B) THE CHANGE in energy is positive.therefore it must be moving from an area of low potential enegry to a high potential enegry.the are around positive charge is high potential area.therefore it must be moving from a negative place(low potential energy) to positive place(high potential energy).(NEGATIVE TO POSITIVE)

(C) E=V/D=6/(4*10^-3) =1500 v/m.

(D)Start by working out the force on the electron caused by the electric field - then subtract the effect of gravity to get the net Force F.

Then from Newton, Force = mass * acceleration (you have F & look up 'm' & this gives you 'a') ...

Then use S(distance) = ut + 1/2 a t^2 (you know S, assume u=0, have 'a' from above so can work out t)

Having found 't' you can calculate velocity from v = a * t

F = q*E
m*a = q*E

a = q*E/m = 1.6*10^-19*1000/9.1*10^-31 = 1.758*10^14 m/s^2

v^2-u^2 = 2*a*s

v = sqrt(2*a*s)

= sqrt(2*1.758*10^14*0.1*10^-2)

= 5.93*10^5 m/s

(E)

Work = change in electric potential. The formula for electric potential is given by V = (k * q1 * q2) / r. Note that the work will be negative since like charges repel:

W = (k * q1 * q2) / r
W = (8.9875 * 10^9 * -0.0000014 * -0.0000014) / 0.009
W = 2.246875 J

Round to 2 significant figures and make negative since the charges are repelling each other:

W = -2.2 J

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