Two large conducting plates are placed 2 mm apart. The bottom plate is attached

Question

Two large conducting plates are placed 2 mm apart. The bottom plate is attached to ground so that its electrical potential is 0 V. The top plate is kept at a positive potential of 1000 V.
(a) Which plate is positively charged?
(b) What is the magnitude and direction of the electric field?
Magnitude V/m
direction
(c) A 1 g mass carries a negative charge of -4 µC and is places exactly at the center between the two plates. What is its potential energy? J
(d) If the mass in part (c) is initially at rest and then released, which plate does the mass hit?
(e) What is the velocity of the mass in part (d) just before it hits the plate? m/s

Explanation / Answer

a) the plate which is at 1000 V is positively chrged

b) v = e.d =>    1000 = E.(2/1000)

E = 2*106 volt/m

from +ve plate to -ve plate , toward plate which is grounded

c) potential = work done to carry -ve charge half the way = (1/1000)*(4)*(10-6)*(2*106) = -0.008 J

if -ve charge is picked from -ve plate and tried to move towards + plate half the way

d) it hits the +ve plate

e) chnage in P.E = change in K.E

   (1/2)*(1/1000)*v*v = 8/1000

v*v =   16*106

v =4 m/sec

LIFESAVER !!!!

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