electricity

• what symbol is this

  open switch

  
• what symbol is this

  closed switch

  
• what symbol is this

  lamp

  
• what symbol is this

  voltmeter

  
• what symbol is this

  ammeter

  
• what symbol is this

  resistor

  
• what symbol is this

  ldr

  
• what symbol is this

  thermistor

  
• what symbol is this

  variable resistor

  
• what symbol is this

  diode

  
• what symbol is this

  led

  
• what symbol is this

  fuse

  
• what symbol is this

  cell

  
• what symbol is this

  battery

  
• how is an ammeter used

  in series
• how is a voltmeter used

  in parallel
• what is charge measured in

  coulombs
• what is pd

  energy transferredd per unit charge
• current is directly proportional to ..........

  potential difference
• what iv graph is this

  resistor

  
• what iv graph is this

  filament bulb

  
• what iv graph is

  diode

  
• describe a series current

  -current is same everywhere

  -potential difference shared

  -total resitance = all resistance added up
• describe a parallel circuit

  -current splits at junction(total -sum of branch currents)

  -pd -same across each branch

  total resistance decreases as more branches added
• resistors in circuit

  series-add up resistance

  parallel-resistance drops due to extra paths
• national grid

  uses step up transformers to increase voltage -(reduce energy loss in cables )

  uses step down transformers to reduce voltage to safe levels for homes
• what is the uks mains supply

  230v ,50 hz AC
• what is a alternating current

  changes direction (used in mains)
• what is direct current

  flows in 1 direction (used in batteries)
• what is the live wire

  brown -230 v
• neutral wire

  blue -completes circuit
• earth wire

  green /yellow -safety -carries current if there is a fault
• is the live wire dangerous when switch off

  yes since it stills carries voltage
• what does a fuse do

  melt is current is too high
• what does circuit breaker do

  switch off circuit if current too high
• static electricity

  a build up of charge by friction

  electrons transfer -one becomes negatively charged

  -opposites attract
• how does a spark happen

  when the pd is high enough to cause the air to ionise
• what is an electric field

  a region around a charged object when it can exert a force
• field lines

  go away when positive

  go towards when negative