electric field exercise

2/

3/
3.1/

3.2/ If a positive point charge were placed at the point outside the shell and released
from rest, it would
(a) move away from the origin.
(b) move toward the origin.
(c) remain at rest.
4/ A solid spherical insulator has radius R = 2.5 cm, and carries a total positive charge Q
= 8 × 10-10 C distributed uniformly throughout its volume.


a) Find the magnitude of the electric field |E| at a radius of 5 cm from the
origin (i.e., outside the sphere).
(a)
(b)
(c)
(d)
(e)

|E| = 2.88×103 N/C
|E| = 8.92×103 N/C
|E| = 2.41×104 N/C
|E| = 5.01×104 N/C
|E| = 8.30×104 N/C

b) What is the potential V at a radius of 2 cm from the origin?
(  0 =8.86 10-10 c2/Nm2 )

5. A positive point charge q = +3 μC is placed on the y axis at y = +5 cm. A negative
point charge -q = -3 μC is placed at the origin.

a) Calculate the work done by the field to bring in an additional point charge +q from
infinity to the point A. (The other two charges are held in position during this procedure.)
(a)
(b)
(c)
(d)

W = 2.98 J
W = 0.47 J
W=0J
W = -1.36 J

(e) W = -5.19 J


b) What is the potential energy U of the square arrangement of charges?

6/

7. 2 Particles with charges q1=8 μC, q2=-6 μC, place at A,B respectively, AB=8 cm.
Calculate the vector electric field induce by q1, q2 at M, know: MA=8 cm, MB=6 cm
8. 3 electric charges QA = -5.10-8 C, QB = 16.10-8, QC = 9.10-8C place at A,B,C of the
triangle ABC (AB=8 CM, AC= 6 cm, BC =10 CM). Calculate the angle create by the
electric force affect to QA and AB of triangle ABC