Welcome to Physics 102

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Welcome to Physics 102!

• Electricity Magnetism
• Optics
• Atomic Physics
• Nuclear Physics
• Relativity

http//online.physics.uiuc.edu/courses/phy
s102/
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Meet the Lecturer

• Tim Stelzer tstelzer_at_uiuc.edu
• Research
• Theoretical Elementary Particle Physics
• Physics Education
• Office Hours Monday 11-12.

http//online.physics.uiuc.edu/courses/phys102/
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Course Format(Spiral Learning)

• Preflights 50
• Homework 100
• Lab (Prelab due at start of lab) 150
• Discussion 150
• Take-home quizzes drop lowest 1
• Hour Exams (3 x 100) 300
• Final Exam 250
• 
  1000

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Grading Scale

• 950-1000 A
• 920-949 A
• 900-919 A-
• 880-899 B
• 860-879 B
• 835-859 B-

• 810-834 C
• 780-809 C
• 750-779 C-
• 720-749 D
• 690-719 D
• 610-689 D-
• lt610 F

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Prelectures Lecture

• Do it!
• Answer preflights 50/1000 points
• 1 point for honest attempt at preflight.
• 1 point for using clicker in lecture (75)
• 2 points/lecture x 25 lectures 50 points

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P102 Lectures

• Not everything you need!
• Concepts, Connections, Motivation
• Comprehensive Textbook
• Calculations Homework Discussion
• Hands-On Lab
• Taking Notes
• Lecture notes are available at bookstore or
  online
• Some key pieces for you to fill in

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Physics 101
Content
Physics 102
Macroscopic
Microscopic

• ElectricityMag
• Circuits
• Optics
• Modern
• Atomic
• Nuclear
• Relativity

• Kinematics
• Forces
• Energy
• Fluids
• Waves (Sound)

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Origin of Charge

• Charge is an intrinsic property of matter
• Two types
• Positive Charge Protons
• Negative Charge electrons
• Opposites Attract! (likes repel)
• Atoms are neutral
• Negatively charged electrons orbit r10-10 m
• Positively charged central nucleus r10-15 m

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Conductors and Insulators
A
A
Most things are in between perfect conductor /
insulator
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Separating Charge

• Triboelectric friction
• Conduction contact
• Induction proximity/ground

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Electroscope

• Conduction
• Charged rod is brought near scope
• Charged rod touches scope transferring some
  charge
• Scope is left w/ same charge as rod
• Induction
• Charged rod is brought near scope
• Scope is briefly grounded allowing charge to flow
  on (or off) scope
• Scope is left w/ opposite charge as rod

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ACTS

• A negatively charged rod is used to charge an
  electroscope by induction. What is the resulting
  net charge on the electroscope?

A) positive B) zero C) negative

• If the conducting electroscope were replaced by
  an insulating ball and then charged by induction
  as above, what would be the net charge on the
  ball.

A) positive B) zero C) negative
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Coulombs Law

• Example

• Magnitude of the force between charges q1 and q2
  separated a distance r
• F k q1q2/r2 k 9x109 Nm2/C2
• Force on electron in Hydrogen atom

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Coulombs Law

• Example

• Magnitude of the force between charges q1 and q2
  separated a distance r
• F k q1q2/r2 k 9x109 Nm2/C2
• Force on electron in Hydrogen atom

F
F (9x109)(1.6x10-19)(1.6x10-19)/(10-10)2 N
2.3x10-8 N
(to the left)
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ACT Coulombs Law

• What is the direction of the force on the proton
  due to the electron?
• (A) Left (B) Right (C) Zero
• What is the magnitude of the force on the proton
  due to the electron?

• Example

F 2.3x10-8 N
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ACT
A positive and negative charge with equal
magnitude are connected by a rigid rod, and
placed near a large negative charge. What is the
net force on the two connected charges?
A) Left B) Zero C) Right
Positive charge is attracted (force to left)
Negative charge is repelled (force to right)
Positive charge is closer so force to left is
larger.
-

-
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ACT Induced Dipole

• An uncharged conducting sphere is hung next to a
  charged sphere. What happens when the uncharged
  sphere is released?

• 1) Nothing
• 2) Attracted to charged sphere.
• 3) Repelled from charged sphere.

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ACT Induced Dipole

• An uncharged conducting sphere is hung next to a
  charged sphere. What happens when the uncharged
  sphere is released?

• 1) Nothing
• 2) Attracted to charged sphere.
• 3) Repelled from charged sphere.

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ACT Induced Dipole

• An uncharged conducting sphere is hung next to a
  charged sphere. What happens when the uncharged
  sphere is released?

1) Negative charge attracts repels -
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ACT Induced Dipole

• An uncharged conducting sphere is hung next to a
  charged sphere. What happens when the uncharged
  sphere is released?

1) Negative charge attracts repels -
2) Since is closer, attractive force is
strongest
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ACT Induced Dipole

• An uncharged conducting sphere is hung between a
  charged sphere and a grounded sphere and held
  midway between the two. What happens when the
  uncharged sphere is released?

• An uncharged conducting sphere is hung between a
  charged sphere and a grounded sphere and held
  midway between the two. What happens when the
  uncharged sphere is released?

1) Negative charge attracts repels 2) Since
is closer, attractive force is strongest
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To Do

• Read Sections 16.1-6
• Do your preflight before 800 AM on the day of
  lecture.

See you Monday!