Edexcel IGCSE Physics 复习笔记 2.2.2 Voltage in Series & Parallel

• In a series circuit:
  • The current is the same at all points ie. through each component
  • The total potential difference of the power supply is shared between the components

   

Lamps connected in a series circuit

• In the above circuit:
  • The current from the power supply is the same as the current in both lamps I = I₁ = I₂
  • If the battery is marked 12 V, then the potential difference would be 12 ÷ 2 = 6 V across each lamp

   

• In a parallel circuit:
  • The total current through the whole circuit is the sum of the currents through the separate components
  • The potential difference across each component is the same

   

Lamps connected in a parallel circuit

• In the above circuit:
  • Because the current splits up, the sum of currents in each branch will equal the current from the power supply I = I₁ + I₂
  • If the battery is marked 12 V, then the potential difference would be 12 V across each lamp

   

Series Circuits

• A series circuit consists of a string of two or more components connected in a loop
• The advantages of a series circuit are:
  • All of the components can be controlled by a single switch
  • Fewer wires are required

   

• The disadvantages of a series circuit are:
  • The components cannot be controlled separately
  • If one component breaks, they will all stop working as well

   

In the series circuit above, only one switch is needed to control all of the lamps. This can be seen as an advantage or as a disadvantage

Parallel Circuits

• A parallel circuit consists of two or more components attached across different branches of the circuit
• The advantages of a parallel circuit are:
  • The components can be individually controlled, using their own switches
  • If one component breaks, then the others will continue to function

   

• The disadvantages of a parallel circuit are:
  • Many more wires involved so much more complicated to set up
  • All components have the same voltage as the supply, so harder to control if components need to have different voltages

   

In the parallel circuit above, the lamps are connected in parallel and can be switched on and off by their own switch