Circuit systems

• Switch (open)


  Used to turn a circuit off

  
• Switch (closed)


  Used to turn a circuit on

  
• Cell (electrical)


  Provides the energy for a circuit

  
• Battery


  Two or more cells connected together

  
• Diode


  A device that allows current to flow in one direction only

  
• Resistor (fixed)


  A device that restricts or limits the flow of current

  
• Variable resistor


  A device that has a slider which can be moved to change the resistance

  
• LED (light-emitting diode)


  A diode which emits light and is much more efficient than a filament bulb

  
• Lamp (filament bulb)


  A device containing a filament in a bulb that heats up when a current flows so that it emits light

  
• Fuse


  A safety device consisting of a strip of wire that melts, breaking an electric circuit, if too much current passes through it

  
• Voltmeter


  A device placed in parallel with a component to measure the potential difference (voltage) across it

  
• Ammeter


  A device placed in series with a component to measure the current through it

  
• Themistor


  A device whoseresistance decreasesas the surroundingtemperature increases

  
• LDR (light-dependent resistor)


  A device whoseresistance decreasesas the surroundinglight intensity increases