Components in Series & Parallel Circuits

Voltage in series

• The total voltage of the supply is shared between the components in a series loop:

V_supply = V₁ + V₂ + V₃ + …

• The share that each component takes is set by its resistance:
  • Two identical components in series each take half the supply voltage
  • A component with higher resistance takes the larger share of the supply voltage
  • A component with lower resistance takes the smaller share
• This is why a high-resistance bulb in series with a low-resistance wire glows brightly while the wire stays cool: the bulb is dissipating most of the supply's energy because most of the voltage is dropped across it

Voltage on parallel branches

• Every parallel branch sits between the same two junction points; the voltage across one branch therefore matches the voltage across any other branch, and both equal the supply voltage:

V_supply = V_branch1 = V_branch2 = …

• This is because the two ends of every branch are joined to the same two points (the two junctions), and the potential difference between two fixed points is one number whatever route you take between them
• A consequence: any single branch in a parallel circuit will run at its normal "rated" voltage if it is rated to match the supply; this is why household appliances are wired in parallel

Advantages and disadvantages of each wiring