What is Electromagnetism? Introduction in Pictures

Branislav K. NikolićDepartment of Physics and Astronomy, University of Delaware, U.S.A.

PHYS 208 Honors: Fundamentals of Physics IIhttp://www.physics.udel.edu/~bnikolic/teaching/phys208/phys208.html

PHYS 208 Honors: What is Electromagnetism?

Electromagnetism: Fundamentals

PHYS 208 Honors: What is Electromagnetism?

Electromagnetism: Applications

PHYS 208 Honors: What is Electromagnetism?

Origin of Charged Objects: Elementary Particles, Standard Model, and All That

PHYS 208 Honors: What is Electromagnetism?

Fundamental Forces Between Elementary Particles

PHYS 208 Honors: What is Electromagnetism?

History of Elementary Particles

PHYS 208 Honors: What is Electromagnetism?

Coulomb Force vs. Gravitational Force

1 2Coulomb1 on 2 2 on 1 2

0

1

4Coulomb q q

F Frπε

= = 1 21 on 2 2 on 1 2

gravity gravity m mF F G

r= =

2electron on proton 39

electron on proton 0

110

4

Coulomb

electrongravity

electron proton

F q

F Gm mπε= ∼

PHYS 208 Honors: What is Electromagnetism?

Expressing Force Action Through Field

on at ( , , )( , , ) q x y zFE x y z

q=

PHYS 208 Honors: What is Electromagnetism?

Examples of Gravitational Fields

PHYS 208 Honors: What is Electromagnetism?

Electric Field of Point Charges

PHYS 208 Honors: What is Electromagnetism?

Where Does Magnetism Come From?

�Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits – magnetic field sources are essentially dipolar in nature, having a north and south magnetic pole.

(Ga,Mn)As

PHYS 208 Honors: What is Electromagnetism?

How strong is “Magnetic” Force?

LorentzF qE= +� �

v�

v�

1 on 2 20

(2)4

electric qF q q E

rπε= =

�

q q1 2

1 on 2 2

(2)(2)magnetic vE

F q vB q vc

= =�

03

(2)4

qv rB

r

µπ

×=� �

�

30

1(2)

4

qE r

rπε=

� �

r�

0 0 2

(2)(2) (2)

v EB v E

cε µ ×= × =

��� �

qv B��

1 on 2

1 on 2

2magnetic

electric

F v

cF

=

�

�2410

for two copper

wires

−≈

PHYS 208 Honors: What is Electromagnetism?

Electric vs. Magnetic vs. Electromagnetic Field

0 02

E E v Bv c v E

B Bc

′ = + ×

⇒ ×′ = −

� � ��

��≪ � �

�Electric and magnetic fields are not invariant entities themselves, but are aspects of a single entity, the electromagnetic field, which manifests itself differently to different moving observers.

PHYS 208 Honors: What is Electromagnetism?

Electrodynamics: Electromagnetic Waves