Experiments

• Ohms Law:

  Connect a voltmeter parallel to a resistor and a ammeter in series with a variable resistor

  Vary the resistance of the variable resistor to change the p.d of the circuit

  measure I with a ammeter

  measure V with a voltmeter

  repeat with multiple readings in equal intervals

  Plot graph V against I

  should be a straight line through the origin

  Resistance is the gradient of the graph

  
• Experiment to determine Resistivity:

  Measure the diameter using a micrometer and take multiple readings along the length of the wire + calculate average

  Vary length, L

  measure V with voltmeter

  measure I with ammeter

  Calculate R for each length using V = I * R

  Plot graph of R against L

  Graph should be a straight line through the origin

  gradient = Resistivity/area

  Resistivity = gradient * area

  
• Resistivity increases with temperature as there are more collisions between conducting electrons and positive ions