SlideShare a Scribd company logo
UCSD Physics 10
Electromagnetism
Electromagnetic Induction
Electromagnetic Waves
James Clerk Maxwell Michael Faraday
UCSD Physics 10
Spring 2008 2
Electromagnetism
• Electricity and magnetism are different facets of
electromagnetism
– a moving electric charge produces magnetic fields
– changing magnetic fields move electric charges
• This connection first elucidated by Faraday, Maxwell
• Einstein saw electricity and magnetism as frame-
dependent facets of unified electromagnetic force
UCSD Physics 10
Spring 2008 3
Magnetic fields from electricity
• A static distribution of charges produces an electric
field
• Charges in motion (an electrical current) produce a
magnetic field
– electric current is an example of charges (electrons) in motion
UCSD Physics 10
Spring 2008 4
Electromagnets
• Arranging wire in a coil and running a current
through produces a magnetic field that looks a lot
like a bar magnet
– called an electromagnet
– putting a real magnet inside, can shove the magnet back
and forth depending on current direction: called a
solenoid
UCSD Physics 10
Spring 2008 5
Induced Current
• The next part of the story is that a changing
magnetic field produces an electric current in a
loop surrounding the field
– called electromagnetic induction, or Faraday’s Law
UCSD Physics 10
Spring 2008 6
The Electromagnetic Connection
• A changing magnetic field produces an electric field, and a
changing electric field produces a magnetic field.
• Electric and Magnetic fields can produce forces on charges
• An accelerating charge produces electromagnetic waves
(radiation)
• Both electric and magnetic fields can transport energy
– Electric field energy used in electrical circuits, e.g., released in
lightning
– Magnetic field carries energy through transformer, for example
UCSD Physics 10
Spring 2008 7
Electromagnetic Radiation
• Interrelated electric and magnetic fields traveling through space
• All electromagnetic radiation travels at c = 3108 m/s in
vacuum – the cosmic speed limit!
– real number is 299792458.0 m/s exactly
UCSD Physics 10
Spring 2008 8
What’s “Waving” in EM waves?
• What medium transports sound waves?
– Can there be sound waves in the vacuum of outer space?
• What medium transports water waves?
• What medium transports radio waves?
• A topic of considerable debate in the late 1800’s and early
1900’s
• Led to the concept of the “luminiferous ether” – an invisible
“jello” that was thought to vibrate electromagnetically
• Experiments that sought this ether didn’t find it!
• This was quite a surprise
Electromagnetic waves travel through empty space!
UCSD Physics 10
Spring 2008 9
Examples of Electromagnetic Radiation
• AM and FM radio waves (including TV signals)
• Cell phone communication links
• Microwaves
• Infrared radiation
• Light
• X-rays
• Gamma rays
• What distinguishes these from one another?
UCSD Physics 10
Spring 2008 10
Uses of Electromagnetic Waves
• Communication systems
– One-way and two-way
• Radar
• Cooking (with microwaves)
• Medical Imaging (X rays)
• “Night Vision” (infrared)
• Astronomy (radio, wave, IR, visible, UV, gamma)
All that we experience through our eyes is conveyed by
electromagnetic radiation…
UCSD Physics 10
Spring 2008 11
The Electromagnetic Spectrum
• Relationship between frequency, speed and
wavelength
f ·l = c
f is frequency, l is wavelength, c is speed of light
• Different frequencies of electromagnetic radiation
are better suited to different purposes
• The frequency of a radio wave determines its
propagation characteristics through various media
UCSD Physics 10
Spring 2008 12
US Frequency Allocation – the FCC
(300 MHz has a wavelength of 1 meter)
“Radio” frequency-space is allocated to the hilt!
Here’s a sample region from 300–600 MHz
International allocation gets tricky
UCSD Physics 10
Spring 2008 13
Generation of Radio Waves
• Accelerating charges radiate EM energy
• If charges oscillate back and forth, get time-varying fields
E
+
+
+
-
-
-
+
-
-
+
-
-
-
+
+
+
UCSD Physics 10
Spring 2008 14
Generation of Radio Waves
If charges oscillate back and forth, get time-varying magnetic fields
too
Note that the magnetic fields are perpendicular to the electric field
vectors
B
+
+
+
-
-
-
+
-
-
+
-
-
-
+
+
+
UCSD Physics 10
Spring 2008 15
Polarization of Radio Waves
E
Transmitting
antenna
UCSD Physics 10
Spring 2008 16
Reception of Radio Waves
Receiving antenna works best
when ‘tuned’ to the
wavelength of the signal, and
has proper polarization
Electrons in antenna are “jiggled”
by passage of electromagnetic wave
E
Optimal antenna length is one quarter-wavelength (l/4)
UCSD Physics 10
Spring 2008 17
Questions
Why are car radio antennas vertical?
Why are cell phone antennas so short?
How do polarizing sunglasses work?
UCSD Physics 10
Spring 2008 18
Assignments
• Read Chapter 31 for Friday
• Q/O #4 due 5/23 by midnight
• HW 6 due 5/23: 22.E.1, 22.E.5, 22.E.11, 22.E.16,
22.E.20, 22.E.30, 22.E.33, 22.P.1, 23.E.3, 26.E.7,
26.E.9, 26.E.11

More Related Content

Similar to 18_electromagnetism.ppt

electromagnetic_waves.ppt
electromagnetic_waves.pptelectromagnetic_waves.ppt
electromagnetic_waves.ppt
mragarwal
 
Electromagnetic_Waves.ppt
Electromagnetic_Waves.pptElectromagnetic_Waves.ppt
Electromagnetic_Waves.ppt
JosephMuez2
 
PHY PUC 2 Notes-Electromagnetic waves
PHY PUC 2 Notes-Electromagnetic wavesPHY PUC 2 Notes-Electromagnetic waves
PHY PUC 2 Notes-Electromagnetic waves
study material
 
Electro 0
Electro 0Electro 0
Electro 0Omed
 
Electro 0
Electro 0Electro 0
Electro 0zanko99
 
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptxWHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
Goutham Vanam
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
AryanSingh12A1440
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
osamazahid13
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
RyanAnderson41811
 
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjs
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjsMagnetism_Electromagntism jsjemsjjssjsjsjsjsjs
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjs
milesiandaligdig
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
MVNandan
 
electromag.ppt
electromag.pptelectromag.ppt
electromag.ppt
Miladrazi1
 
Electromagnetic Waves Class 12
Electromagnetic Waves Class 12 Electromagnetic Waves Class 12
Electromagnetic Waves Class 12 Self-employed
 
Lesson 12 Radio waves.pptx
Lesson 12 Radio waves.pptxLesson 12 Radio waves.pptx
Lesson 12 Radio waves.pptx
danielloberiz1
 
Waves classic to quantum
Waves classic to quantumWaves classic to quantum
Waves classic to quantumzehnerm2
 
Chapter2-Structure of Atom 2023.pptx
Chapter2-Structure of Atom 2023.pptxChapter2-Structure of Atom 2023.pptx
Chapter2-Structure of Atom 2023.pptx
ValarmathiRajendran1
 
Electromagnetic waves
Electromagnetic wavesElectromagnetic waves
Electromagnetic waves
harshbharti6
 
orientation ppt emwtl .ppt
orientation ppt emwtl .pptorientation ppt emwtl .ppt
orientation ppt emwtl .ppt
SatyanarayanaMoturiM
 
Introduction to electromagnetic exploration method
Introduction to electromagnetic exploration methodIntroduction to electromagnetic exploration method
Introduction to electromagnetic exploration method
oilandgas24
 

Similar to 18_electromagnetism.ppt (20)

electromagnetic_waves.ppt
electromagnetic_waves.pptelectromagnetic_waves.ppt
electromagnetic_waves.ppt
 
Electromagnetic_Waves.ppt
Electromagnetic_Waves.pptElectromagnetic_Waves.ppt
Electromagnetic_Waves.ppt
 
Physics
PhysicsPhysics
Physics
 
PHY PUC 2 Notes-Electromagnetic waves
PHY PUC 2 Notes-Electromagnetic wavesPHY PUC 2 Notes-Electromagnetic waves
PHY PUC 2 Notes-Electromagnetic waves
 
Electro 0
Electro 0Electro 0
Electro 0
 
Electro 0
Electro 0Electro 0
Electro 0
 
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptxWHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
WHAT IS ELECTROMAGNETIC WAVE THEORY.pptx
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
 
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjs
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjsMagnetism_Electromagntism jsjemsjjssjsjsjsjsjs
Magnetism_Electromagntism jsjemsjjssjsjsjsjsjs
 
Mag-electromag.ppt
Mag-electromag.pptMag-electromag.ppt
Mag-electromag.ppt
 
electromag.ppt
electromag.pptelectromag.ppt
electromag.ppt
 
Electromagnetic Waves Class 12
Electromagnetic Waves Class 12 Electromagnetic Waves Class 12
Electromagnetic Waves Class 12
 
Lesson 12 Radio waves.pptx
Lesson 12 Radio waves.pptxLesson 12 Radio waves.pptx
Lesson 12 Radio waves.pptx
 
Waves classic to quantum
Waves classic to quantumWaves classic to quantum
Waves classic to quantum
 
Chapter2-Structure of Atom 2023.pptx
Chapter2-Structure of Atom 2023.pptxChapter2-Structure of Atom 2023.pptx
Chapter2-Structure of Atom 2023.pptx
 
Electromagnetic waves
Electromagnetic wavesElectromagnetic waves
Electromagnetic waves
 
orientation ppt emwtl .ppt
orientation ppt emwtl .pptorientation ppt emwtl .ppt
orientation ppt emwtl .ppt
 
Introduction to electromagnetic exploration method
Introduction to electromagnetic exploration methodIntroduction to electromagnetic exploration method
Introduction to electromagnetic exploration method
 

More from AbeyuAssefa

Chapter 9 Machine Installation in maintenance.ppt
Chapter 9 Machine Installation in maintenance.pptChapter 9 Machine Installation in maintenance.ppt
Chapter 9 Machine Installation in maintenance.ppt
AbeyuAssefa
 
Chap 3-Gears in maintenance technology.pdf
Chap 3-Gears in maintenance technology.pdfChap 3-Gears in maintenance technology.pdf
Chap 3-Gears in maintenance technology.pdf
AbeyuAssefa
 
Chap 5 Elements of Maint Techenologyf.ppt
Chap 5 Elements of Maint Techenologyf.pptChap 5 Elements of Maint Techenologyf.ppt
Chap 5 Elements of Maint Techenologyf.ppt
AbeyuAssefa
 
Chap 1 (Introduction to maintenance final.ppt
Chap 1 (Introduction to maintenance final.pptChap 1 (Introduction to maintenance final.ppt
Chap 1 (Introduction to maintenance final.ppt
AbeyuAssefa
 
Chap 8 Organization of Maintenance Resources.ppt
Chap 8 Organization of Maintenance Resources.pptChap 8 Organization of Maintenance Resources.ppt
Chap 8 Organization of Maintenance Resources.ppt
AbeyuAssefa
 
construction of dc generator.pptx
construction of dc generator.pptxconstruction of dc generator.pptx
construction of dc generator.pptx
AbeyuAssefa
 
Unit7-DC_Motors.ppt
Unit7-DC_Motors.pptUnit7-DC_Motors.ppt
Unit7-DC_Motors.ppt
AbeyuAssefa
 
smps last.pptx
smps last.pptxsmps last.pptx
smps last.pptx
AbeyuAssefa
 
DC-machines.ppt
DC-machines.pptDC-machines.ppt
DC-machines.ppt
AbeyuAssefa
 
18_electromagnetism.ppt
18_electromagnetism.ppt18_electromagnetism.ppt
18_electromagnetism.ppt
AbeyuAssefa
 

More from AbeyuAssefa (10)

Chapter 9 Machine Installation in maintenance.ppt
Chapter 9 Machine Installation in maintenance.pptChapter 9 Machine Installation in maintenance.ppt
Chapter 9 Machine Installation in maintenance.ppt
 
Chap 3-Gears in maintenance technology.pdf
Chap 3-Gears in maintenance technology.pdfChap 3-Gears in maintenance technology.pdf
Chap 3-Gears in maintenance technology.pdf
 
Chap 5 Elements of Maint Techenologyf.ppt
Chap 5 Elements of Maint Techenologyf.pptChap 5 Elements of Maint Techenologyf.ppt
Chap 5 Elements of Maint Techenologyf.ppt
 
Chap 1 (Introduction to maintenance final.ppt
Chap 1 (Introduction to maintenance final.pptChap 1 (Introduction to maintenance final.ppt
Chap 1 (Introduction to maintenance final.ppt
 
Chap 8 Organization of Maintenance Resources.ppt
Chap 8 Organization of Maintenance Resources.pptChap 8 Organization of Maintenance Resources.ppt
Chap 8 Organization of Maintenance Resources.ppt
 
construction of dc generator.pptx
construction of dc generator.pptxconstruction of dc generator.pptx
construction of dc generator.pptx
 
Unit7-DC_Motors.ppt
Unit7-DC_Motors.pptUnit7-DC_Motors.ppt
Unit7-DC_Motors.ppt
 
smps last.pptx
smps last.pptxsmps last.pptx
smps last.pptx
 
DC-machines.ppt
DC-machines.pptDC-machines.ppt
DC-machines.ppt
 
18_electromagnetism.ppt
18_electromagnetism.ppt18_electromagnetism.ppt
18_electromagnetism.ppt
 

Recently uploaded

Chapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptxChapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptx
Mohd Adib Abd Muin, Senior Lecturer at Universiti Utara Malaysia
 
Embracing GenAI - A Strategic Imperative
Embracing GenAI - A Strategic ImperativeEmbracing GenAI - A Strategic Imperative
Embracing GenAI - A Strategic Imperative
Peter Windle
 
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
Levi Shapiro
 
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
MysoreMuleSoftMeetup
 
TESDA TM1 REVIEWER FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
TESDA TM1 REVIEWER  FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...TESDA TM1 REVIEWER  FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
TESDA TM1 REVIEWER FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
EugeneSaldivar
 
A Strategic Approach: GenAI in Education
A Strategic Approach: GenAI in EducationA Strategic Approach: GenAI in Education
A Strategic Approach: GenAI in Education
Peter Windle
 
Polish students' mobility in the Czech Republic
Polish students' mobility in the Czech RepublicPolish students' mobility in the Czech Republic
Polish students' mobility in the Czech Republic
Anna Sz.
 
Unit 8 - Information and Communication Technology (Paper I).pdf
Unit 8 - Information and Communication Technology (Paper I).pdfUnit 8 - Information and Communication Technology (Paper I).pdf
Unit 8 - Information and Communication Technology (Paper I).pdf
Thiyagu K
 
The Challenger.pdf DNHS Official Publication
The Challenger.pdf DNHS Official PublicationThe Challenger.pdf DNHS Official Publication
The Challenger.pdf DNHS Official Publication
Delapenabediema
 
Synthetic Fiber Construction in lab .pptx
Synthetic Fiber Construction in lab .pptxSynthetic Fiber Construction in lab .pptx
Synthetic Fiber Construction in lab .pptx
Pavel ( NSTU)
 
Digital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and ResearchDigital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and Research
Vikramjit Singh
 
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCECLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
BhavyaRajput3
 
Honest Reviews of Tim Han LMA Course Program.pptx
Honest Reviews of Tim Han LMA Course Program.pptxHonest Reviews of Tim Han LMA Course Program.pptx
Honest Reviews of Tim Han LMA Course Program.pptx
timhan337
 
Model Attribute Check Company Auto Property
Model Attribute  Check Company Auto PropertyModel Attribute  Check Company Auto Property
Model Attribute Check Company Auto Property
Celine George
 
The approach at University of Liverpool.pptx
The approach at University of Liverpool.pptxThe approach at University of Liverpool.pptx
The approach at University of Liverpool.pptx
Jisc
 
Francesca Gottschalk - How can education support child empowerment.pptx
Francesca Gottschalk - How can education support child empowerment.pptxFrancesca Gottschalk - How can education support child empowerment.pptx
Francesca Gottschalk - How can education support child empowerment.pptx
EduSkills OECD
 
Lapbook sobre os Regimes Totalitários.pdf
Lapbook sobre os Regimes Totalitários.pdfLapbook sobre os Regimes Totalitários.pdf
Lapbook sobre os Regimes Totalitários.pdf
Jean Carlos Nunes Paixão
 
Instructions for Submissions thorugh G- Classroom.pptx
Instructions for Submissions thorugh G- Classroom.pptxInstructions for Submissions thorugh G- Classroom.pptx
Instructions for Submissions thorugh G- Classroom.pptx
Jheel Barad
 
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
Nguyen Thanh Tu Collection
 
special B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdfspecial B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdf
Special education needs
 

Recently uploaded (20)

Chapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptxChapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptx
 
Embracing GenAI - A Strategic Imperative
Embracing GenAI - A Strategic ImperativeEmbracing GenAI - A Strategic Imperative
Embracing GenAI - A Strategic Imperative
 
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
 
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
Mule 4.6 & Java 17 Upgrade | MuleSoft Mysore Meetup #46
 
TESDA TM1 REVIEWER FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
TESDA TM1 REVIEWER  FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...TESDA TM1 REVIEWER  FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
TESDA TM1 REVIEWER FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
 
A Strategic Approach: GenAI in Education
A Strategic Approach: GenAI in EducationA Strategic Approach: GenAI in Education
A Strategic Approach: GenAI in Education
 
Polish students' mobility in the Czech Republic
Polish students' mobility in the Czech RepublicPolish students' mobility in the Czech Republic
Polish students' mobility in the Czech Republic
 
Unit 8 - Information and Communication Technology (Paper I).pdf
Unit 8 - Information and Communication Technology (Paper I).pdfUnit 8 - Information and Communication Technology (Paper I).pdf
Unit 8 - Information and Communication Technology (Paper I).pdf
 
The Challenger.pdf DNHS Official Publication
The Challenger.pdf DNHS Official PublicationThe Challenger.pdf DNHS Official Publication
The Challenger.pdf DNHS Official Publication
 
Synthetic Fiber Construction in lab .pptx
Synthetic Fiber Construction in lab .pptxSynthetic Fiber Construction in lab .pptx
Synthetic Fiber Construction in lab .pptx
 
Digital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and ResearchDigital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and Research
 
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCECLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
 
Honest Reviews of Tim Han LMA Course Program.pptx
Honest Reviews of Tim Han LMA Course Program.pptxHonest Reviews of Tim Han LMA Course Program.pptx
Honest Reviews of Tim Han LMA Course Program.pptx
 
Model Attribute Check Company Auto Property
Model Attribute  Check Company Auto PropertyModel Attribute  Check Company Auto Property
Model Attribute Check Company Auto Property
 
The approach at University of Liverpool.pptx
The approach at University of Liverpool.pptxThe approach at University of Liverpool.pptx
The approach at University of Liverpool.pptx
 
Francesca Gottschalk - How can education support child empowerment.pptx
Francesca Gottschalk - How can education support child empowerment.pptxFrancesca Gottschalk - How can education support child empowerment.pptx
Francesca Gottschalk - How can education support child empowerment.pptx
 
Lapbook sobre os Regimes Totalitários.pdf
Lapbook sobre os Regimes Totalitários.pdfLapbook sobre os Regimes Totalitários.pdf
Lapbook sobre os Regimes Totalitários.pdf
 
Instructions for Submissions thorugh G- Classroom.pptx
Instructions for Submissions thorugh G- Classroom.pptxInstructions for Submissions thorugh G- Classroom.pptx
Instructions for Submissions thorugh G- Classroom.pptx
 
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
BÀI TẬP BỔ TRỢ TIẾNG ANH GLOBAL SUCCESS LỚP 3 - CẢ NĂM (CÓ FILE NGHE VÀ ĐÁP Á...
 
special B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdfspecial B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdf
 

18_electromagnetism.ppt

  • 1. UCSD Physics 10 Electromagnetism Electromagnetic Induction Electromagnetic Waves James Clerk Maxwell Michael Faraday
  • 2. UCSD Physics 10 Spring 2008 2 Electromagnetism • Electricity and magnetism are different facets of electromagnetism – a moving electric charge produces magnetic fields – changing magnetic fields move electric charges • This connection first elucidated by Faraday, Maxwell • Einstein saw electricity and magnetism as frame- dependent facets of unified electromagnetic force
  • 3. UCSD Physics 10 Spring 2008 3 Magnetic fields from electricity • A static distribution of charges produces an electric field • Charges in motion (an electrical current) produce a magnetic field – electric current is an example of charges (electrons) in motion
  • 4. UCSD Physics 10 Spring 2008 4 Electromagnets • Arranging wire in a coil and running a current through produces a magnetic field that looks a lot like a bar magnet – called an electromagnet – putting a real magnet inside, can shove the magnet back and forth depending on current direction: called a solenoid
  • 5. UCSD Physics 10 Spring 2008 5 Induced Current • The next part of the story is that a changing magnetic field produces an electric current in a loop surrounding the field – called electromagnetic induction, or Faraday’s Law
  • 6. UCSD Physics 10 Spring 2008 6 The Electromagnetic Connection • A changing magnetic field produces an electric field, and a changing electric field produces a magnetic field. • Electric and Magnetic fields can produce forces on charges • An accelerating charge produces electromagnetic waves (radiation) • Both electric and magnetic fields can transport energy – Electric field energy used in electrical circuits, e.g., released in lightning – Magnetic field carries energy through transformer, for example
  • 7. UCSD Physics 10 Spring 2008 7 Electromagnetic Radiation • Interrelated electric and magnetic fields traveling through space • All electromagnetic radiation travels at c = 3108 m/s in vacuum – the cosmic speed limit! – real number is 299792458.0 m/s exactly
  • 8. UCSD Physics 10 Spring 2008 8 What’s “Waving” in EM waves? • What medium transports sound waves? – Can there be sound waves in the vacuum of outer space? • What medium transports water waves? • What medium transports radio waves? • A topic of considerable debate in the late 1800’s and early 1900’s • Led to the concept of the “luminiferous ether” – an invisible “jello” that was thought to vibrate electromagnetically • Experiments that sought this ether didn’t find it! • This was quite a surprise Electromagnetic waves travel through empty space!
  • 9. UCSD Physics 10 Spring 2008 9 Examples of Electromagnetic Radiation • AM and FM radio waves (including TV signals) • Cell phone communication links • Microwaves • Infrared radiation • Light • X-rays • Gamma rays • What distinguishes these from one another?
  • 10. UCSD Physics 10 Spring 2008 10 Uses of Electromagnetic Waves • Communication systems – One-way and two-way • Radar • Cooking (with microwaves) • Medical Imaging (X rays) • “Night Vision” (infrared) • Astronomy (radio, wave, IR, visible, UV, gamma) All that we experience through our eyes is conveyed by electromagnetic radiation…
  • 11. UCSD Physics 10 Spring 2008 11 The Electromagnetic Spectrum • Relationship between frequency, speed and wavelength f ·l = c f is frequency, l is wavelength, c is speed of light • Different frequencies of electromagnetic radiation are better suited to different purposes • The frequency of a radio wave determines its propagation characteristics through various media
  • 12. UCSD Physics 10 Spring 2008 12 US Frequency Allocation – the FCC (300 MHz has a wavelength of 1 meter) “Radio” frequency-space is allocated to the hilt! Here’s a sample region from 300–600 MHz International allocation gets tricky
  • 13. UCSD Physics 10 Spring 2008 13 Generation of Radio Waves • Accelerating charges radiate EM energy • If charges oscillate back and forth, get time-varying fields E + + + - - - + - - + - - - + + +
  • 14. UCSD Physics 10 Spring 2008 14 Generation of Radio Waves If charges oscillate back and forth, get time-varying magnetic fields too Note that the magnetic fields are perpendicular to the electric field vectors B + + + - - - + - - + - - - + + +
  • 15. UCSD Physics 10 Spring 2008 15 Polarization of Radio Waves E Transmitting antenna
  • 16. UCSD Physics 10 Spring 2008 16 Reception of Radio Waves Receiving antenna works best when ‘tuned’ to the wavelength of the signal, and has proper polarization Electrons in antenna are “jiggled” by passage of electromagnetic wave E Optimal antenna length is one quarter-wavelength (l/4)
  • 17. UCSD Physics 10 Spring 2008 17 Questions Why are car radio antennas vertical? Why are cell phone antennas so short? How do polarizing sunglasses work?
  • 18. UCSD Physics 10 Spring 2008 18 Assignments • Read Chapter 31 for Friday • Q/O #4 due 5/23 by midnight • HW 6 due 5/23: 22.E.1, 22.E.5, 22.E.11, 22.E.16, 22.E.20, 22.E.30, 22.E.33, 22.P.1, 23.E.3, 26.E.7, 26.E.9, 26.E.11

Editor's Notes

  1. 05/19/08
  2. 05/19/08
  3. 05/19/08
  4. 05/19/08
  5. 05/19/08
  6. 05/19/08
  7. 05/19/08
  8. 05/19/08
  9. 05/19/08
  10. 05/19/08
  11. 05/19/08
  12. 05/19/08
  13. 05/19/08
  14. 05/19/08
  15. 05/19/08
  16. 05/19/08
  17. 05/19/08
  18. 05/19/08