Section 2 Electricity


Series and parallel circuits

  • Components in an electrical circuit can be connected one after another (in series) or side by side (in parallel).

Series circuits

  • There is only one path for the current in a series circuit.
  • The current is the same at all points in a series circuit:

    = I1 = I2 
    I = supply current as measured by an ammeter

    (The various meters are assumed not to be part of the circuit as they are simply there to measure values and have no effect on the circuit.)

  • The supply voltage Vs is equal to the sum of the voltages across each individual component in a series circuit:

    Vs= V1 + V2 
    Vs = supply voltage
  • The combined total resistance of resistors connected in a series circuit is the sum of the individual resistances. The current in the series circuit depends on the combined resistance of all of the components.
  • A practical example of a series circuit is a simple flashlight consisting of a battery, a switch and a lamp.
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