Electric Current and its Effects

• Symbols of Electric Components

  • Electric Cell
    • Longer line: Positive terminal ($+$)
    • Shorter, thicker line: Negative terminal ($-$)
  • Electric Bulb
    • Filament inside connected to terminals
  • Switch (Key)
    • ON position: Connected
    • OFF position: Disconnected
  • Battery
    • Combination of two or more cells
    • Positive terminal of one connected to negative of another

• Heating Effect of Electric Current

  • Principle
    • Wire gets hot when current passes through it
    • Depends on material, length, and thickness
  • Applications
    • Electric Heater (Room heater, water heater)
    • Electric Iron
    • Hair Dryer
  • Electric Fuse
    • Safety device preventing damage
    • Made of special wires that melt quickly and break
    • MCB (Miniature Circuit Breakers): Switch off automatically on overload

• Magnetic Effect of Electric Current

  • Oersted's Discovery
    • Compass needle deflects when current flows nearby wire
  • Electromagnet
    • Coil of insulated wire wrapped around an iron piece
    • Acts as a magnet when electric current flows through it
    • Used in electric bells, cranes to lift heavy iron scrap

• Electric Bell

  • Components
    • Electromagnet
    • Iron strip with a striker
    • Contact screw
    • Gong
  • Working
    • Current flows $\rightarrow$ Electromagnet attracts iron strip $\rightarrow$ Striker hits gong $\rightarrow$ Circuit breaks $\rightarrow$ Contact breaks $\rightarrow$ Cycle repeats rapidly