2.1.4 Required Practical: Investigating Resistance

• Typical factors affecting resistance

  • The length of the conductor
  • The cross-sectional area of the conductor
  • The material of the conductor
  • The temperature of the conductor
• Equipment Needed

  • Power Supply
  • Ammeter
  • Voltmeter
  • Variable Resistor (Rheostat)
  • Wires
  • Conductor Samples
  • Micrometer or Caliper
  • Clamp Stand and Crocodile Clips
• Investigating the Effect of Length on Resistance

  1. Connect power supply, ammeter, voltmeter

  2. Choose wire material and cross-sectional area

  3. Measure specific length of wire

  4. Set power supply to constant voltage

  5. Record current and potential difference

  6. Calculate resistance using Ohm’s Law

  7. Repeat for different lengths

  8. Plot graph of resistance against length
• Investigating the Effect of Cross-Sectional Area on Resistance

  1. Use wires of same material and length

  2. Connect wires in circuit setup

  3. Measure and record current and potential difference

  4. Calculate resistance for each wire

  5. Plot graph of resistance against inverse of cross-sectional area
• Investigating the Effect of Material on Resistance

  1. Use wires of different materials

  2. Connect wires in circuit setup

  3. Measure and record current and potential difference

  4. Calculate resistance for each wire

  5. Compare resistances of different materials
• Safety Considerations

  • Avoid Overheating
  • Check Connections
  • Handle Equipment Carefully
• Ensure that the power supply is not set to a high voltage that might overheat the conductor
• Ensure all connections are secure to prevent short circuits
• Handle the ammeter, voltmeter, and other equipment with care to avoid damage and ensure accurate readings
• Data Analysis

  1. Expect direct proportionality where resistance increases with length

  2. Expect inverse proportionality where resistance decreases with increasing cross-sectional area

  3. Compare resistances to determine material effects
• Summarize how each factor affects resistance based on experimental data and graphical analysis
• Discuss any sources of error and how they might be minimized in future experiments
• Ohm’s Law


  R=V/I
• Resistance Proportionality

  • Resistance increases with length
  • Resistance decreases with cross-sectional area
  • Different materials have different resistivities
• Ensure measurements are accurate and repeat experiments to obtain reliable data