11 coulomb's law notes
TRANSCRIPT
Coulom
b’s Law
• Charles Coulomb (1736-1806: French)–Studied relationship between
force and charge• SI unit of charge = 1 coulomb (C)
–NOT charge of 1 e- (1.6 x 10-19)–Charge of 6.24 x 1018 e-
•We’ll get real definition later
1 Coulomb is about how many electrons flow through a 100 W light bulb every second.
Co
ulo
mb
’s La
w
• The LAW!– Force directly related to magnitude of
the charges– Force inversely related to the square of
the distance between the two charges
F = r2
kqQF α q Q
r2
1F α
r2
q QF α
F= r2k qQ
• Coulomb’s Law: Should look familiar
Only Attractive
Attractive or Repulsive
F= r2G mM Product of
masses
Product of charges
Both areinverse-square
laws
Large Magnitude9 x 109 N·m2/C2
Small Magnitude 6.67 x 10-11 N·m2/kg2
Coulom
b’s Law
F= r2k q Q
• Sample problem 0! YEAH!–A negative charge of -5.3μC and a
positive charge of 12 μC are separated by 0.69 m. What is the force of attraction between the two of them?
(9 x 109)=
(5.3 x 10-
6)(0.69)2
F= 1.2 N
(12 x 10-6)
(Remember that μ means 10-6 and n means 10-9)
Coulom
b’s Law
F= r2k q Q
• Sample problem 1! YEAH!–What is the magnitude of the
electrostatic force between 2 protons in the nucleus? (assume the distance to be 3.0x10-13 cm)
(9 x 109)=
(1.6 x 10-
19)(3.0 x 10-15 )
2
F=25.6 N
(1.6 x 10-
19)
Coulom
b’s Law
F= r2k q Q
• Sample problem 1! YEAH!–What is the magnitude of the
electrostatic force between 2 protons in the nucleus? (assume the distance to be 3.0x10-13 cm)
(9 x 109)=
(1.6 x 10-
19)(3.0 x 10-15 )
2
F=25.6 N
(1.6 x 10-
19)