Circuit Symbols

• What do we need to know to draw circuit diagrams?

  The functions and symbols of components
• What is the purpose of a cell or battery in a circuit?

  To provide electric power to the circuit
• What does a switch do in a circuit?

  Controls the flow of electricity
• What happens when a switch is open?

  The circuit is effectively turned off
• What are filament lamps?

  Small bulbs used in circuits
• What is the function of a fuse in a circuit?

  Breaks if too much current flows
• What is a diode's function in a circuit?

  Allows current to flow in one direction
• What is a light emitting diode (LED)?

  A diode that emits light when current flows
• Where are LEDs commonly found?

  In alarm clocks and traffic lights
• What do ammeters measure in a circuit?

  Current
• How are ammeters connected in a circuit?

  In series
• What do voltmeters measure in a circuit?

  Potential difference
• How are voltmeters connected in a circuit?

  In parallel
• What are the two types of basic resistors?

  Fixed and variable resistors
• What is a light dependent resistor (LDR)?

  A resistor whose resistance depends on light intensity
• How does an LDR behave in bright light?

  It has low resistance allowing high current flow
• What applications use LDRs?

  Automatic night lights and burglar alarms
• How does an LDR respond to darkness?

  Resistance increases, limiting current flow
• What is a thermistor?

  A resistor whose resistance depends on temperature
• How does the resistance of a thermistor change with temperature?

  Higher temperatures decrease resistance
• What are common uses for thermistors?

  Temperature receptors in engines and thermostats
• What are the main components and their functions in a circuit?

  • Cell/Battery: Provides electric power
  • Switch: Controls electricity flow
  • Filament Lamp: Acts as a light source
  • Fuse: Breaks circuit with excess current
  • Diode: Allows current in one direction
  • LED: Emits light when current flows
  • Ammeter: Measures current in series
  • Voltmeter: Measures potential difference in parallel
  • Resistors: Control current flow
• What are the differences between LDRs and thermistors?

  • LDRs:
  • Resistance decreases in bright light
  • Used in night lights and alarms
  • Thermistors:
  • Resistance decreases with higher temperature
  • Used in engines and thermostats