Resistance

• Steps to carr=
• Describe the setup of the practical

  
• The resistance of the wire is........... to the length

  directly proportional

  
• Issues about this practical

  small resistance when length of wire is 0

  -> this shouldn't be there and is a problem due to the method

  
  

  if the temperature of the wire increases, then the resistance will also increase
• What is a zero error

  A reading on a measuring instrument when the value should be zero

  this is a systematic error

  -> cannot reduce it by carrying out repeats
• Why does this error occur?


  extremely difficult to get crocodile clip with a 0cm position on the ruler

  
• a second reason why this zero error occurs

  there is also some resistance caused by the contact between the crocodile clip and the wire
• How to prevent the temperature of the wire increasing?

  • Use a low potential difference, which will keep the current low, reducing any heating in the wire

  
  

  • only turn on the current when taking a reading (turn off the current between readings)
• Steps for activity 1 p1

  Set up the circuit - add a voltmeter in parral + an ammeter in series + a power pack Attach a meter ruler with a wire, where the resistor is, use crocodile clips to attach the meter ruler/wire to circuit place the crocodile clips so they are 100cm apart
• Steps for activity 1 p2

  Turn on power pack to 4V + Measure both the PD and the Current record in table Turn off power pack reduce the length of wire between crocodile clips by 10cm Repeat for a wire lengths down to 10cm
• Activity 1 p3

  Be careful- the wire may get hot. Turn off the power pack if the wire starts glowing or smoking Calculate the resistance for each length of wire (using equation R= V/I) Record values of resistance in a table

  polt a graph, resistance in ohms on y-axis, length of wire in cm on x-axis
• Activity 2 - investigating resistors in series and in parallel p1

  set up a circuit with ammeter in series + a voltmeter in parallel + a power pack + 2 resistors in series

  turn on power pack at 4v Measure pd across power pact
• Activity 2 p2

  Calculate the total resistance of the circuit with resistors in series Set up the circuit for two resistors in parallel repeat steps 2-4 for the resistors in parallel calculate total resistance of the circuit with resistors in parallel