Circuits

• circuit symbols

  A) open switch

  B) closed switch

  C) cell

  D) battery

  E) diode

  F) resistor

  G) variable resistor

  H) LED

  I) lamp

  J) fuse

  K) voltmeter

  L) ammeter

  M) thermistor

  N) LDR

  
• LDR

  • light dependent resistor
  • dependent on intensity of light
  • bright light - resistance falls
  • darkness - resistance at its highest
  • used in automatic night lights and burglar detectors
• thermistor

  • temperature dependent resistance
  • hot conditions - resistance drops
  • cool conditions - resistance goes up
  • make useful temperature detectors
• LDR's and thermistors can be used in sensing circuits to turn on and increase power based on conditions they are in
• series circuit

  
• parallel circuit

  
• a series circuit has one loop where a parallel circuit has 2 or more loops
• in a series circuit

  • potential difference is shared between components
  • V total = V1 + V2+ V3...
  • current is the same everywhere
  • I1 = I2 = I3 ...
  • resistance adds up
  • R total = R1 + R2
• in a parallel circuit

  • potential difference is the same across all components
  • V1 = V2 = V3
  • current is shared between branches
  • I total = I1 + I2 + I3 ...
  • resistance is reduced if resistor is added
• resistance in a series circuit

  
• resistance in a parallel circuit