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Circuit Diagrams

Series circuits
  • In a series circuit, voltage is not the same in each part of the circuit.
  • \(V_{T}=V_{1}+V_{2}\)
  • However the current is the same in all parts of the circuit.
  • Resistance is defined as \(R_{T}=R_{1}+R_{2}\)
Parallel Circuits
  • In a parallel circuit, the voltage is the same across the circuit, however the current is not the same.
  • Current is given by the equation: \(I_{T}=I_{1}+I_{2}\)
  • Resistance is inverted: \(\frac{1}{R_{T}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}\)
  • We can also use: \(R_{T}=\frac{R_{1}\times R_{2}}{R_{1}+R_{2}}\)
TIP: Restistors in parallel
  • If two resistors are in parallel, and they have the same resistance, then you can just half the value of one of them.
  • E.G. Two 2 ohm resistors in parallel give a total resistance of 1 ohm.
  • E.G. Two 840 ohm resistors in parallel give a total resistance of 420 ohms.
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