mproton = 0.000 000 000 000 000 000 000 000 001 6748 kg

melectron=0.000 000 000 000 000 000 000 000 000 0009 kg

mproton = 1836melectron

1e qe =1.602101019 Coulomb

How many electrons are there in 1 Coulomb of negative charge?

How many protons are there in 1 Coulomb of positive charge?

Three pith balls are suspended from thin threads.Various objects are charged (rubbing glass againstpolyester, nylon against silk, rubber against fur, etc)and each pith ball is charged by touching them withone of these objects.

It is found that pith balls A and B repel each otherand 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.

Three pith balls are suspended from thin threads.Various objects are charged (rubbing glass againstpolyester, nylon against silk, rubber against fur, etc)and each pith ball is charged by touching them withone of these objects.

It is found that pith balls A and B attract each otherand 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.

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

4

2

3

What force exists between two concentrations of charge, each 1 coulomb separated center-to-center by 1 meter?

)C/Nm109875.8( 229221

R

qqkF

( 1 C )( 1 C )

(1 m2)

= 2,020,390,000 lbs= 1,010,195 tons

0.2248 lb/N= 8.9875109 N

= 15o

assume 2 equally charged balloons (with uniformly distributed charge)

0.8 grams each

W 0.008 N

0.75 meters

0.75 m

x

BALLOON’SWEIGHT

STRING’STENSION

ELECTROSTATICREPULSION

W

T

F

T

F

W

W T

Felectric

We can calculate the tan by

1) T/F2) T/W3) F/T4) F/W5) W/F6) W/T

W T

Felectric

With tan15o=Felectric

W

Felectric=(0.008 N)tan15o

= 2.14410-3 N

W 0.008 N

R = 0.388 meters

0.002144 N =(8.9875109 Nm2/C2) q1q2

(0.388 m)2

A hydrogen atom is composed of a nucleus containing asingle proton, about which a single electron orbits. Theelectrical force between the two particles is 2.31039 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.