Circuits

• Circuit symbols


  Established set of symbols used in all circuit diagrams
• Series circuits


  • Only one path around the circuit
  • If one component breaks, all others stop working
  • More bulbs in series decrease brightness of all
  • Switches control all bulbs together
• Parallel circuits


  • More than one path around the circuit
  • If one component breaks, others stay on
  • More bulbs added in parallel are same brightness
  • Switches (on branches) control bulbs individually
• Current


  Flow of electrons (charged particles) around a circuit
• Ammeter


  Measures current, connected in series with circuit
• In a series circuit, current is the same everywhere
• In a parallel circuit, current splits and divides down each branch
• Potential difference (voltage)


  Difference in charge between positive and negative ends of cell/battery
• In a series circuit, voltage is shared out between components
• In a parallel circuit, each branch receives the same voltage as power supply
• Series circuit


  Electrical components connected one after another in a single loop
• Series circuits


  • Current is the same through each component
  • Total potential difference of the power supply is shared between the components
  • Total resistance of the circuit is the sum of individual resistors
• If one of the bulbs is broken then current will not be able to flow round the circuit
• If one bulb goes out, they all go out
• Ammeter


  A device used to measure electric current
• In a series circuit, an ammeter will measure the same current wherever it is placed in the circuit
• Potential difference


  The potential difference (or voltage) of a supply is a measure of the energy given to the charge carriers in a circuit. Units = volts (V). This is the voltage between two points that makes an electric current flow between them.
• In a series circuit

  The total potential difference of the power supply is equal to the sum of the potential differences across all other components
• Resistance


  The opposition in an electrical component to the movement of electrical charge through it. Resistance is measured in ohms.
• If resistors are connected in series


  The total resistance of the circuit is the sum of the individual resistors
• In a series circuit, the current is the same through each component
• Parallel circuits


  Electrical components are connected alongside one another, forming extra loops
• Parallel circuits


  • Current will not pass through every component on its way round the circuit
  • If one of the bulbs is broken then current will still be able to flow round the circuit through the other loop
  • If one bulb goes out, the other will stay on
• Current in parallel circuits

  1. Current splits as it leaves the cell and passes through one or other of the loops

  2. Ammeter placed in different parts of the circuit will show how the current splits
• In parallel circuits, the total current supplied is split between the components on different loops
• In parallel circuits, the potential difference is the same across each loop
• In parallel circuits, the total resistance of the circuit is reduced as the current can follow multiple paths
• Electrical current


  Transfers energy around circuits
• Types of current


  • Direct
  • Alternating
• Electrical charge flow


  Causes ions in wires to vibrate more, increasing wire temperature
• One watt is equal to one joule per second (J/s)
• Efficient transmission of power

  • Transmitting energy at high voltage with low current keeps wires cooler and wastes less energy