Electricity%20and%20Magnetism - PowerPoint PPT Presentation

View by Category
Title:

Electricity%20and%20Magnetism

Description:

In E&M, we will deal with forces that depend upon charge ... Franklin's Kite. He flew a kite in a thunderstorm and saw that charge flowed down the string ... – PowerPoint PPT presentation

Number of Views:19
Avg rating:3.0/5.0
Slides: 16
Provided by: LeeCa1
Category:
Tags:
Transcript and Presenter's Notes

Title: Electricity%20and%20Magnetism

1
Electricity and Magnetism
• Physics 102
• Professor Lee Carkner
• Lecture 9

2
Electricity and Magnetism
• In EM, we will deal with forces that depend upon
charge
• Stationary charges exert an electric force
• EM forces only affect charged particles

3
Forces
• The electric force is much stronger than the
gravitational force
• Why dont we feel this strong force?
• Most things have roughly equal numbers of
positive and negative particles
• Like charges repel, opposite attract
• e.g. lightning, static electric shock

4
Plus and Minus
• The basic particle of positive charge is the
proton
• Protons generally dont move
• Electrons are in the shells of atoms and can be
removed
• Adding electrons makes something negative
• All EM forces depend on what the electrons are
doing

5
Using Electricity
• Why is the electrical force important?
• Convert electrical energy into work
• Convert electrical energy into heat and light
• Convert electrical energy into sound
• Electrical energy can be very finely controlled

6
Making Electricity
• Three ways to do this
• Chemically
• Magnetically
• Physically
• Four basic methods friction, conduction,
induction, polarization

7
Triboelectricity
• Rubbing will transfer electrons from one
substance to the other by friction
• Example Glass rubbed with silk becomes positive,
rubber rubbed with fur becomes negative

8
How Does Charge Move?
• Some types of material allow electrons to move
freely (e.g. metals)
• When you charge a conductor, the electrons will
flow through it
• Other types do not allow electrons to flow (e.g.
glass, rubber)
• If you charge them, the charge stays put

9
Conduction
• Both end up with the same sign charge

10
Induction
• Said to be grounded
• If you place a charged object near a grounded
conductor it will repel the same sign charges to
the ground
• Charge is opposite that of the inductor

11
Polarization
• You have charged the balloon but not the wall
• The negative charge on the balloon attracts the
positive charged parts of the molecules of the
wall, polarizing it

12
Polarization
13
Origins of Electricity
• Moving charges by rubbing has been known since
ancient times
• Benjamin Franklin proposed the terms positive and
negative for the two types of charge

14
Franklins Kite
• He flew a kite in a thunderstorm and saw that
charge flowed down the string

15
Next Time