Investigating resistance

• What does resistance depend on in a circuit?

  Factors like length and configuration
• How does the resistance vary with the length of the conductor?

  Resistance increases with longer wire length
• What is the method to investigate resistance based on wire length?

  1. Attach a crocodile clip at 0 cm.
  2. Attach a second clip at a measured distance.
  3. Record current and potential difference (p.d.).
  4. Move the second clip to a new position.
  5. Repeat for various lengths.
  6. Calculate resistance using $R =$$V/I$.
  7. Plot resistance against wire length.
  8. Expect a straight line through the origin.
• What does an ammeter measure?

  Current in amps
• Where must the ammeter be placed in a circuit?

  In series with the component being investigated
• What does a voltmeter measure?

  Potential difference in volts
• Where must the voltmeter be placed in a circuit?

  In parallel around the component being investigated
• What is the formula to calculate resistance?

  $R =$$V/I$
• What does a straight line through the origin on a resistance graph indicate?

  Resistance is directly proportional to length
• What is a systematic error?

  An error that consistently skews results
• What could cause a graph not to go through the origin?

  Systematic error in length measurement
• Why should you be careful with the temperature of the wire?

  Temperature affects resistance measurements
• What are the steps to record measurements in the resistance experiment?

  1. Close the switch to record current and p.d.
  2. Open the switch and move the clip.
  3. Close the switch again to record new measurements.
  4. Repeat for different lengths.