ch. 32 electrostatics electricity at rest. electric forces arise from subatomic particles –...

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Ch. 32 Electrostatics Electricity at rest

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Page 1: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Ch. 32 Electrostatics

Electricity at rest

Page 2: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Electric Forces

• Arise from subatomic particles– Positive nucleus surrounded by negative electrons

Charge: physical property that causes particles to experience a force

2 TYPES: PositiveNegative

Page 3: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:
Page 4: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:
Page 5: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Conservation of Charge

• Since matter is neither created nor destroyed, subatomic particles are neither created not destroyed.

• Subatomic particles may be transferred from one object to another, but overall, charge is conserved!!!

Page 6: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Standard unit of Charge

• Coulomb (C )• The charge of an electron is 1.6 x 10-19 C

Page 7: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

A pair of identical coins are electrically charged. One with a charge of + 15 C and the

other a charge of – 8 C. When they are brought together, what is the charge of each

after contact? • Net Charge = + 15 C – 8 C = 7 C

• The coins are identical, therefore they will share the charge equally. 3.5 C charge for each coin!

Page 8: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Coulomb’s Law• The force between the charges is directly

proportional to the product of their charges and inversely proportional to the distance between

F = k q1q2 k= constant = 9 x109 N m2

d2 C2

q1 = charge 1q2 = charge 2

d = the distance between q1 &

q2

Page 9: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

F = k q1q2

d2

q1 q2

dk = 9.0 x 109 N M2/C2

What other equation does this remind you of????

Page 10: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Practice ProblemF = k q1q2

d2

What is the electrostatic force between a pair of electrons 1 m apart?

k = 9.0 x 109 NM2/C2

The charge of an electron is 1.6 x 10-19 C

Page 11: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Practice ProblemF = k q1q2

d2

What is the electrostatic force between a pair of electrons 1 m apart?

k = 9.0 x 109 NM2/C2

The charge of an electron is 1.6 x 10-19 C

F = (9.0 x 109 N M2/C2 ) (1.6 x 10-19 C) (1.6 x 10-19 C) (1 m)2

F = 2.3 x 10-28 N

Page 12: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

What is the electrostatic force between a 5 x 10-6 C charge and a 3 x 10-8 C charge

that are 0.25 m apart?

Page 13: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

What is the electrostatic force between a 5 x 10-6 C charge and a 3 x 10-8 C charge

that are 0.25 m apart?F = k q1q2

d2

F =

Page 14: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

What is the electrostatic force between a 5 x 10-6 C charge and a 3 x 10-8 C charge

that are 0.25 m apart?F = k q1q2

d2

F = (9.0 x 109 N m2/C2 ) (5 x 10-6 C )(3 x 10-8 C )(0.25 m)2

= 0.0216

Page 15: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Conductors & Insulators

Page 16: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Charging

• 3 Methods that result in charging: – Friction – Contact– Induction

Page 17: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Charging

• Friction: When electrons are transferred by friction from one object to another

• Contact• Induction

Page 18: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Charging

• Friction• Contact: when electrons are transferred from

one object to another by direct contact• Induction

Page 19: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Charging

• Friction• Contact• Induction: when electrons are caused to move by the presence of a nearby charge.

Page 20: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

Charge Polarization

• Occurs in insulators• Rearrangement of the positions of charges within the atoms and molecules

Page 21: Ch. 32 Electrostatics Electricity at rest. Electric Forces Arise from subatomic particles – Positive nucleus surrounded by negative electrons Charge:

The End

• In Class: Practice Problem Solving with coulomb’s Law