topic p2- electricity

• circuit symbols

  • cell
  • switch
  • filament lamp
  • fuse
  • led
  • resistor
  • variable resistor
  • ammeter
  • voltmeter
  • diode
  • ldr
  • thermistor
• cell

  
• switch

  
• filament lamp

  
• fuse

  
• led

  
• resistor

  
• variable resistor

  
• ammeter

  
• voltmeter

  
• diode

  
• ldr

  
• thermistor

  
• current

  current is the flow of electric charge
• charge = current x time

  charge- coulombs

  current- amps

  time- seconds
• Q = I t

  
• current in a circuit

  
• easily understand current

  • current travels through wires via electrons like cars on a road
  • potential difference (or voltage) is what drives the electron, similar to the engine in a car
  • resistance is similar to traffic in the road, slows the flow of current (traffic)
• potential difference = current x resistance

  potential difference- volts

  current- amps

  resistance- ohms
• V = I R

  
• resistance can depend on lots of factors in a circuit

  • this could be based on the strength of a component such as a resistor
  • other components such as filament lamps can cause slight resistance
  • length and diameter of a wire can also change the resistance
• resistance can depend on lots of factors in a circuit

  
• sensing circuits- light dependent resistor (ldr)

  • a light dependent resistor
  • the higher the light intensity, the lower the resistance

  
• sensing circuits- thermistor

  • a temperature dependent resistor
  • the higher the temperature, the lower the resistance

  
• series circuit

  
• parallel circuit

  
• series circuit

  • total p.d is the sum of all p.d in circuit
  • current is the same everywhere
  • total resistance is the sum of all resistances in the circuit
• parallel circuit

  • p.d is the same everywhere in the circuit
  • total current is the sum of all current in the circuit
  • current splits at junctions
  • if two resistors are in parallel, total resistance is less than the smallest resistor
• electricity in the home

  
• power = current x potential difference

  power- watts

  current- amps

  potential difference- volts
• P = I V

  
• electricity in the home- plug

  
• plugs- blue wire

  • neutral wire
  • completes the circuit
• plugs- green and yellow

  • earth wire
  • grounds the wire for safety
• plugs- brown

  • live wire
  • carries the current
• the national grid

  
• the national grid

  • power stations produce electricity
  • step-up transformers increase the voltage to reduce the current, this reduces resistance in the wires
  • pylons carry the current across the country
  • step-down transformers decrease the voltage back to a safe amount
  • the electricity is delivered to homes