Electricity

Static electricity

charge 电荷

electron 电子 (-) 能动 Atom

• nucleus 荷
  • neutron 中子
  • proton 质子

coulomb 库伦

Insulator 绝缘体

--- Friction

insulated conductor

导体接地消电 如果带正电，会把负电吸回来 如果带负电，会把负电退回去

unlike charges attract 异性相吸 like charges repel 同性相斥 repulsion repulsion attraction attraction neutrally charged attraction

electric field

正电 电场线朝外 负电 电场线朝内

电场线表示正电荷的方向

电场强度随随电场距离增大而减小

平行电极板 parallel charged plate

电流 charge

1. conventional flow
2. flow of electron

formular

• Difinition of charge
• Difinition of Potential difference
• Difinition of resistance : law
• Difinition of Emf
• Resistance , is resistivity 电阻率

Emf : electronmotiveforce 电动势

Resistor

• ohmic resistor
  • L-V graph was a straight line
    • is not gradient, R =
• non-ohmic
  • L-V graph was a curve

电路

元器件

1. 电源
   1. DC : direct current 直流电
      1. cell (dry) 干电池
   2. AC : Alternating current 交流电 o~o
2. resister
   1. fixed resistor
   2. varriable resistor
   3. potential divider
   4. thermister 热敏电阻
   5. Light Dependent Resister (LDR) 光敏电阻
3. 仪表
   1. V
   2. A
4. fuse

串联和并联

• parallel 并联
  • is inversely proportional to
• serirs 串联
  • is directly proportional to
  • 2. if then

Practical electricity

unit of electricity

British standard soket :

	earth (yellow & green, 230V)
neutral (blue, 0 pd.)		live (brown or red, high pd.)

Safe

1. metal casing
2. fuse
   • fuse rating (额定电流)
     • , ,
3. double insulation

---

1. Cannot use electric at water
2. Exposed wire
3. overload, overheat