المسائل التالية تغطى الفصل الأول من المقرر (قانون
المسائل باللون الأحمر لطلبة كلية العلوم
(1) Two protons in a
molecule are separated by a distance of 3.8´10-10m.
Find the electrostatic force exerted by one proton on the other.
(2) A 6.7mC
charge is located 5m from a -8.4mC
charge. Find the electrostatic force exerted by one on the other.
(3) Two fixed charges, +1.0´10-6C
and -3.0´106C, are 10cm
apart. (a) Where may a third charge be located so that no force acts on it?
(b) Is the equilibrium of this third charge stable or unstable?
(4) Each of two small spheres is charged
positively, the combined charge being 5.0´10-5C.
If each sphere is repelled from the other by a force of 1.0N when the
spheres are 2.0m apart, how is the total charge distributed between the
(5) A certain charge Q is to be divided
into two parts, q and Q-q. What is the relationship of
Q to q if the two parts, placed a given distance apart, are to
have a maximum Coulomb repulsion?
(6) A 1.3mC
charge is located on the x-axis at x=-0.5m, 3.2mC
charge is located on the x-axis at x=1.5m, and 2.5mC
charge is located at the origin. Find the net force on the 2.5mC
(7) A point charge q1=
located on the y-axis at y=0.18m, a charge q2=1.6mC
is located at the origin, and a charge q3=3.7mC
is located on the x-axis at x= -0.18m. Find the resultant force on
the charge q1.
(8) Three point charges of 2mC,
7mC, and –4mC
are located at the corners of an equilateral triangle as shown in the figure
2.9. Calculate the net electric force on 7mC
(9) Two free point charges +q and +4q
are a distance 1cm apart. A third charge is so placed that the entire
system is in equilibrium. Find the location, magnitude and sign of the
third charge. Is the equilibrium stable?
(10) Four point charges are situated at the
corners of a square of sides a as shown in the figure 2.10. Find the
resultant force on the positive charge +q.
(11) Three point charges lie along the y-axis.
A charge q1=-9mC
is at y=6.0m, and a charge q2=-8mC
is at y=-4.0m. Where must a third positive charge, q3, be
placed such that the resultant force on it is zero?
(12) A charge q1
is located at x=+2m, y=+2m and a second charge q2=+2.7mC
is located at x=-4m, y=-4m. Where must a third charge (q3>0)
be placed such that the resultant force on q3 will be
(13) Two similar conducting balls of mass m
are hung from silk threads of length l and carry similar charges q
as shown in the figure 2.11. Assume that
q is so small that tanq can
be replaced by sinq. Show that
x is the separation between the balls (b) If l=120cm, m=10g
and x=5cm, what is q?