required practicals

• What can you investigate regarding resistance?

  Factors affecting resistance
• Where must the ammeter be placed in a circuit?

  In series with the test wire
• What does the voltmeter measure?

  Potential difference across the test wire
• How should the voltmeter be connected?

  In parallel around the component being investigated
• What is the method for investigating resistance using crocodile clips?

  1. Attach a crocodile clip at 0 cm.
  2. Attach a second clip 10 cm away.
  3. Close the switch, record current and pd.
  4. Open switch, move second clip 10 cm, repeat.
  5. Measure resistance for each length.
  6. Plot resistance against wire length.
• What should the graph of resistance against wire length look like?

  It should be a straight line
• What does 'I-V characteristics' refer to?

  Graph of current vs. potential difference
• What type of I-V characteristic do linear components have?

  A straight line
• What type of I-V characteristic do non-linear components have?

  A curved line
• What is the method for finding a component's I-V characteristic?

  1. Set up a test circuit with ammeter, voltmeter, component, variable resistor, and cell.
  2. Vary the variable resistor to change current and pd.
  3. Take readings from ammeter and voltmeter.
  4. Reverse current direction by swapping battery wires.
  5. Plot current against voltage for the component.
• What is the method for investigating resistors in series?

  1. Find at least four identical resistors.
  2. Build circuit with one resistor, record pd.
  3. Measure current and calculate resistance.
  4. Add another resistor in series.
  5. Measure current and calculate overall resistance.
  6. Repeat until all resistors are added.
  7. Plot number of resistors against total resistance.
• What is the method for investigating resistors in parallel?

  1. Build initial circuit with one resistor.
  2. Measure total current and calculate resistance.
  3. Add another resistor in parallel.
  4. Measure current and calculate overall resistance.
  5. Repeat until all resistors are added.
  6. Plot number of resistors against total resistance.
• What happens to total resistance when adding resistors in series?

  Total resistance increases
• What happens to overall resistance when adding resistors in parallel?

  Overall resistance decreases
• How does current behave when resistors are added in parallel?

  Current increases