1. 1e  qe =1.6021010-19 Coulomb mproton = 1836melectron
mproton = kg
melectron= kg
mproton = 1836melectron
1e  qe = 10-19 Coulomb

2. How many electrons are there in
1 Coulomb of negative charge?
How many protons are there in
1 Coulomb of positive charge?

3. Three pith balls are suspended from thin threads.
Various objects are charged (rubbing glass against
polyester, nylon against silk, rubber against fur, etc)
and each pith ball is charged by touching them with
one of these objects.
It is found that pith balls A and B repel each other
and that B and C repel each other.
1) A and C carry charge of opposite sign.
2) A and C carry charge of the same sign.
3) All three carry charge of the same sign.
4) Additional experiments are necessary to
determine the sign of all charges.

4. Three pith balls are suspended from thin threads.
Various objects are charged (rubbing glass against
polyester, nylon against silk, rubber against fur, etc)
and each pith ball is charged by touching them with
one of these objects.
It is found that pith balls A and B attract each other
and that B and C repel each other.
1) A and C carry charge of opposite sign.
2) A and C carry charge of the same sign.
3) All three carry charge of the same sign.
4) Additional experiments are necessary to
determine the sign of all charges.

5. 1 2 3 4 Two uniformly charged spheres are firmly fastened by insulated
stands to frictionless pucks which are set on an air table. The
charge on sphere 2 is 3 the charge on sphere 1. Which force
diagram correctly shows the magnitude and direction of the
electrostatic forces? + + + + + + + + + + + + + + + + + + + + + + + + 1 2 + + + + + + + + + + + + + + + + + + + + + + + + 3 4

6. ( 1 C )( 1 C ) (1 m2) = 8.9875109 N 0.2248 lb/N = 2,020,390,000 lbs
What force exists between two concentrations of charge,
each 1 coulomb separated center-to-center by 1 meter?
( 1 C )( 1 C )
(1 m2)
= 109 N
 lb/N
= 2,020,390,000 lbs
= 1,010,195 tons

7.  = 15o 0.75 meters W  0.008 N 0.8 grams each
assume 2 equally charged
balloons (with uniformly
distributed charge)
 = 15o
0.75 meters
0.8 grams
each
W  N

8. 
0.75 m x

9. 
STRING’S
TENSION
ELECTROSTATIC
REPULSION
BALLOON’S
WEIGHT

10.  F T T W F W

11. Felectric
We can calculate
the tan by W
T/F
T/W
F/T
F/W
W/F
W/T T 

12.  Felectric Felectric Felectric=(0.008 N)tan15o With tan15o= W W T

13. (8.9875109 Nm2/C2) q1q2
(0.388 m)2
N =
R = meters
W  N

14. A hydrogen atom is composed of a nucleus containing a
single proton, about which a single electron orbits. The
electrical force between the two particles is 2.31039
greater than the gravitational force!
If we adjust the distance separating the two particles,
can we find a separation at which the electrical and
gravitational forces are equal?
1) Yes, by moving the particles farther apart.
2) Yes, by moving the particles closer together.
3) No, at any distance.