电磁学（PPT讲稿）Electromagnetism revision

Electromagnetism revision

Electromagnetism revision

Electric fields Chapter 16

Chapter 16 Electric fields

Charge is quantized(量子化). Everything is charged in multiples of e the elementary charge(except quarks

Charge is quantized (量子化). Everything is charged in multiples of e, the elementary charge (except quarks!)

Charge is conserved(守恒的) The total charge of the universe never changes

Charge is conserved (守恒的). The total charge of the universe never changes

Electric field of one point charge E Observation location Source charge 二 丌C 0 Coulombs Law

Electric field of one point charge r r q E ˆ 4 1 2 0     = q Coulomb’s Law

E= q 4 2 g is positive the direction of the field is away from the charge

+ r r q E ˆ 4 1 2 0     = q is positive: the direction of the field is away from the charge

E= q 4 2 g is negative the direction of the field is towards the charge

- r r q E ˆ 4 1 2 0     = q is negative: the direction of the field is towards the charge

Superposition Principle 电场强度叠加原理 F4=geNet t 92V 4(+E2+E 3 1 Location of ge 4 E E ne

Superposition Principle 电场强度叠加原理 - + q1 q2 ( ) 4 1 2 3 4 4 net q E E E F q E      = + + = q + 3 Location of q4 E1  E2  Enet  E3 

Superposition Principle 电场强度叠加原理 In general: net s e +2+b2+ or het s The net field at a location in space is the vector sum of the fields contributed by all charged particles at other locations

Superposition Principle 电场强度叠加原理      Enet = E1 + E2 + E3 + In general: =  i E Ei   net or: The net field at a location in space is the vector sum of the fields contributed by all charged particles at other locations

Dipole 电偶极子 H C Hydrogen chloride Water

-q +q Dipole 电偶极子 d + - Hydrogen chloride + - Water O H H