Electricity

Cards (72)

  • What is current
    Flow of electrical charge
  • When can current flow
    when there is a potential difference
  • What is the unit for current
    ampere
  • What is potential difference
    The force that pushes the charge around the circuit
  • What's the unit for potential difference
    Volt
  • What is resistance
    Anything that slows down the flow of charge
  • What's the unit for resistance
    Ohms
  • What does the current flowing through a component depend on
    The potential difference across it and the resistance of the component.
  • What does a greater resistance cause
    A smaller current
  • What is the size of a current
    The rate of flow of charge
  • What is an ohmic conductor
    The resistance doesn't change with the current
  • How can the current in an ohmic conductor be described
    Directly proportional to the potential difference (at a constant temperature)
  • What happens when electrical charge flows through a filament lamp
    Some energy is transferred to the thermal energy store of the filament
    Resistance increases with temperature
    More current=filament heating up more=higher resistance
  • What happens when electrical charge flows through a diode
    The resistance depends on the direction of the current
    Current can flow through one direction but there's a very high resistance if its reversed
  • What is an I-V characteristic?
    A graph which shows how the current flowing through a component changes as the potential difference across it is increased
  • What's the I-V characteristic of a linear component
    A straight line
  • What's the I-V characteristic of a non linear component
    Curved
  • What is a LDR
    Light dependant resistor
  • What happens to an LDR in bright light
    Resistance falls
  • What happens to an LDR in darkness
    Resistance is higher
  • What are applications of LDRs
    Automatic night lights, outdoor lighting and burglar detectors
  • What is a thermistor?
    A temperature dependant resistor
  • What happens to thermistors in hot conditions
    Resistance drops
  • What happens to thermistors in cold conditions
    Resistance increases
  • What are thermistors used for
    Car engine temperature sensors and electronic thermostats
  • What can sensing circuits be used for?
    To turn on or increase the power to components depending on the conditions that they are in
  • Describe a series circuit
    All components are connected one after the other. If one breaks, charge stops flowing.
  • Describe potential difference in series circuits
    It's shared between the components
    Potential difference around a series circuit will always add up to the source of pd
  • Describe the current in a series circuit.
    Current is the same everywhere
  • What happens when you add a resistor in series
    The resistors have to share the total pd
  • What happens to the total current in a series circuit when a resistor is added
    It's reduced
  • What happens if you remove or disconnect a component in parallel circuits
    It will hardly effect the other components
  • Describe potential difference in parallel circuits
    All the components get the full source pd
  • Describe current in parallel circuits
    The total current is equal to the total of all the currents through the separate components
  • What happens when you add a resistor in parallel
    It reduces the total resistance
  • Why does adding a resistor in parallel reduce the total resistance
    -both resistors have the same potential difference across them
    -by adding another loop the current has more than one direction to go in
    -this increases the total current that can flow round a circuit
    -increase incurrent means decrease in resistance
  • What is alternating current
    The current is constantly changing direction
    they’re produced by alternating potential differences in which the positive and negative ends keep alternating
  • what is direct current
    A current that’s always flowing in the same direction, its created by a direct potential difference
  • what’s the uk mains supply pd and voltage
    230v
    50hz
  • what current do cells and batteries supply
    direct current