ELECTRICITY

• what is this symbol?

  closed switch

  
• what is this symbol?

  open switch

  
• what is this symbol?

  cell

  
• what is this symbol?

  battery

  
• what is this symbol?

  diode

  
• what is this symbol?

  resistor

  
• what is this symbol?

  variable resistor

  
• what is this symbol?

  LED

  
• what is this symbol?

  lamp

  
• what is this symbol?

  fuse

  
• what is this symbol?

  ammeter

  
• what is this symbol?

  thermistor

  
• what is this symbol?

  LDR

  
• what is current?

  the flow of electrical charge - the greater the current the high the rate of flow
• what is current measured in?

  amps

  A

  ammeter
• what is charge measured in?

  coulombs

  C
• what does it mean if the current is the same at all points in the loop?

  as the current in a single closed loop of a circuit has no where else to go
• what is resistance?

  the measure of how it resists the flow of charge
• the higher the resistance...?

  • the more difficult it is for charge to flow
  • the lower the current
• what is resistance measured in?

  Ohm

  Ω
• what is potential difference?

  the difference in electrical potential from one point in a circuit to another
• what is potential difference measured in?

  volts

  V

  voltmeter
• the bigger the potential difference...?

  • the greater the flow of charge through the component
  • the bigger the current
• RP: IV characteristics - METHOD

  1. set up standard test circuit
  2. use variable resistor to adjust the PD across test component
  3. measure voltage and current for a range
  4. repeat experiment at least 3 times to calculate the mean
  5. repeat for other components to be tested
• RP: IV characteristics - VARIABLES

  INDEPENDENT: potential difference across component

  DEPENDENT: current through component
• what is the graph for?

  fixed resistor

  
• describe the resistor graph?

  • current is directly proportional to potential difference at a constant temperature
  • resistance remains constant as current changes
• what is the graph?

  filament lamp

  
• describe the filament lamp graph?

  • as current increases so does the temperature
  • this causes resistance to increase
• what is the graph?

  diode

  
• describe the graph of a diode?

  current only flows in one direction

  diode has very high resistance in reverse direction
• RP: resistance - VARIABLES

  INDEPENDENT: length of wire

  DEPENDENT: resistance

  CONTROL: current
• what does a thermistor do?

  • resistance of a thermistor decreases as temperature increases
  • makes useful where temperature control is required
• what does an LDR do?

  • resistance of LDR decreases as light intensity increases
  • makes useful where automatic light control is needed
• how are electrical components connected in a circuit?

  Series or parallel
• series circuit?

  • same current through each component
  • the total potential difference of the power supply is shared between components
  • the total resistance of two components is the sum of the resistance of each component - this is because the current has to travel through each component in turn
  • adding resistors in series increases the total resistance
• parallel circuit?

  • the potential difference across each component is the same
  • the total current drawn from the power supply is the sum of the currents through the separate components
  • the total resistance of two resistors is less than the resistance of the smallest individual resistor - this is because in parallel there are mire paths for current to take - it can take one or the other allowing it to flow more easily
  • adding resistors in parallel reduces the total resistance
• what does the power of a device depend on?

  the potential difference across it and the current flowing through it

  • a device with a higher potential difference or current will use more energy per second than one with a lower potential difference or current so it will be more powerful
• what is direct current (DC)?

  • has a direct potential difference - one that is always positive or always negative - this makes the current direction constant
  • is the type if current that is supplied by cells and batteries
• what is alternating current (AC)?

  • has an alternating potential difference - one that alternates from positive to negative - this makes the current direction alternate
  • is the type of current used in mains electricity