Final Exam Review
Static Electricity
Coulomb’s Law
Electric Fields

Static Electricity
• Key Point: Occurs when one object takes electrons from another.
• Example: Rubbing your hair with a balloon.
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Coulomb’s Law
•
• Formula:
F elec
= k
C
(q
1 q
2
)/r 2
• The force between two charges q
1 separated by a distance r.
and q
2
,
• k
C is a constant and equals 8.99 x10 9 Nm 2 /kg 2

Elementary Charge
• The charge on either 1 proton OR 1 electron is:
• 1.60 x 10 -19 C for a Proton
• -1.60 x 10 -19 C for an Electron

Example
• The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 E-11 m. Find the magnitude of the electric force between the particles.

Example
• The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 E-11 m. Find the magnitude of the electric force between the particles.
• Givens: r = 5.3 E-11 m q
1
=1.6E-19 C
• k
C
=8.99E9 Nm 2 /s 2 q
2
=-1.6E-19 C

Example
• The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 E-11 m. Find the magnitude of the electric force between the particles.
• Givens: r = 5.3 E-11 m q
1
=1.6E-19 C
• k
C
=8.99E9 Nm 2 /s 2 q
2
=-1.6E-19 C
• F elec
= k
C
(q
1 q
2
)/r 2

Example
• The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 E-11 m. Find the magnitude of the electric force between the particles.
• Givens: r = 5.3 E-11 m q
1
=1.6E-19 C
• k
C
=8.99E9 Nm 2 /s 2 q
2
=-1.6E-19 C
• F elec
= k
C
(q
1 q
2
)/r 2
• F elec
= 8.99E9 (1.6E-19 * -1.6E-19) / (5.3E-11) 2
• F elec
= -8.2 E-8 N

• Pg 566- Practice A
• #2a, 3
Practice

Electric Field Mapping- Examples
• 1 electron and 1 proton
-q
+q

Electric Field Mapping- Examples
• 2 Protons
+q
+q

Electric Field Mapping- Examples
• 2 Electrons
-q
-q