paper 1

• current is the measure of the flow of electrons around the circuit, measured in amps by an ammeter
• potential difference is the driving force of the flow of electrons and is measures in volts by a voltmeter
• resistance is everything at opposes the flow of electrons and is measured in ohms
• an alternating current changes direction
• a direct current doesn't change dircetion
• is a series circuit what is shared?

  potential difference
• is a series circuit what is the same everywhere?


  current
• a series circuit only has one loop
• in a parallel circuit what is shared?

  current
• in a parallel circuit what is the same in each component?

  potential difference
• a parallel circuit has more than one loop
• in a parallel circuit, the loops with a higher resistance have lower current
• the more components in a parallel circuit the lower the resistance
• in a series circuit the sum of the resistance in each component is the total resistance
• how does the neutral wire complete the circuit?


  it carries the current away
• what is the potential difference of the neutral wire?

  0v
• what is the potential difference of the earth wire?

  0v
• what does the earth wire do?

  stops the appliance becoming live if the live wire touches the casing as it provides an alternating pathway for current to flow
• what colour is the earth wire?

  green and yellow
• what colour is the neutral wire?

  blue
• what colour is the live wire?

  brown
• what is the potential difference of the live wire?

  230v
• where does the live wire get the current from?

  mains supply
• why is each wire made of copper?

  conduct electricity
• why does a step up transformer increase the voltage?

  so current is kept low so less energy is lost as heat to the surroundings
• what does a step up transformer increase?

  voltage to 400,000
• what does a step down transformer do?

  decreases voltage to 230v for safety
• when does electricity peak?

  in the late afternoon
• what is a surge?

  a sudden increase in current
• what can surges cause?

  fires, damage appliance, electrical shock
• why is a high pressure dangerous?

  risk of explosion
• what do fuses and circuit breakers do?

  break the circuit if the current is too high
• what is the a fuse connected to?

  live wire
• what does a fuse do if a high current passes through it?

  melts
• why can fuses be costly?


  have to be replaced after each use
• why are circuit breakers better than fuses?


  don't have to be replaced after each use
• what can someone do to prevent electrical shock?

  -use earthing (an earth wire)

  -double insulating appliances (less likely to need an earth wire)
• how do fossil fuels and nuclear power stations work?

  generate thermal energy with turns water into steam which turns a turbine then generates kinetic energy which can be converted into electrical energy and sent across the national grid
• how are ammeters connected?

  in series
• how are voltmeters connected?

  in parallel