general

• potential difference (V) is measured in volts
• filament lamps - as temperature increases, resistance increases
• diodes - current can only flow in one direction
• ohmic conductors - current is directly proportional to potential difference
• filament lamp

  
• ohmic conductors

  
• static electricity - charged object produces an electric field around itself (field lines point from positive to negative)
• rubbing insulating materials together rubs electrons off one material and onto the other (material gaining electrons becomes negatively charged)
• earth wire (green and yellow stripes) - prevents appliances from becoming live
• neutral wire (blue) - completes the circuit
• live wire (brown) - mains electricity voltage is 230V
• power lines transport current at very high voltages higher voltage reduces energy loss
• step up transformers - voltage increases (used between power stations and power lines)
• alternating current - direction of current flow continually changes
• parallel circuits - current is split between branches and the potential difference across each branch is the same
• charge (Q) can only flow if there is a source of potential difference
• resistance (R) is measured in ohms
• current (I) is the rate of flow of charge
• current (I) is measured in amps
• power (W) is the rate of energy transfer
• switch (open)

  
• cell (single)

  
• resistor (not variable)

  
• LED - light emitting diode

  
• voltmeter .

  
• thermistor .

  
• step up transformers increase the voltage and decrease the current
• The electric power is transmitted via the national grid at low current which minimises power loss. 
• Step down transformers decrease the voltage and increase the current near our homes
• A rectifier is a component that turns an alternating current into a direct current
• a resistor whose resistance decreases when temperature increases is a thermistor
• variable resistor allows us to easily adjust its resistance
• For wires and resistors, increasing the temperature will increase the resistance
• charge is a measure ot the total current that flowed within a period of time
• in a light dependent resistor, resistance varies with light intensity
• brown wire = live wire
• In a series circuit, components with a greater resistance will always have a greater share of the voltage
• the earth wire is connected to the casing of the appliance
• If the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow.
• how earth wire protects from electrical shocks:

  1. The earth wire is connected to the casing of the appliance.
  2. If the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow.
  3. This way, we don't get an electric shock from touching the live appliance casing.