Circuits

• What is the focus of Part A of the study material?

  Investigating the relationship between voltage, current, and resistance
• What are the basic steps of the practical in Part A?

  1. Set up a circuit with a voltmeter and ammeter
  2. Increase voltage and record potential difference and current
  3. Swap resistor for a filament lamp and repeat
  4. Plot a graph of current against potential difference
• What is the first step in setting up the circuit?

  Attach a voltmeter in parallel to a resistor
• What should you do after recording the initial voltage and current values?

  Slowly increase the voltage
• What should you do after testing the resistor?

  Swap the resistor for a filament lamp
• What is the purpose of plotting a graph in this practical?

  To visualize the relationship between current and potential difference
• What two types of meters are needed in the circuit?

  Voltmeter and ammeter
• How should the voltmeter be connected in the circuit?

  In parallel to the component
• How should the ammeter be connected in the circuit?

  In series with the component
• What component can be used to alter potential difference?

  A rheostat or variable resistor
• What is an 'Ohmic Conductor'?

  A conductor where current and voltage are proportional
• What condition must be met for a conductor to be considered Ohmic?

  Temperature must remain constant
• What must be kept constant to ensure reliable results in the experiment?

  Temperature should remain constant
• How can you achieve constant temperature during the experiment?

  Disconnect the supply when not taking readings
• How does temperature affect resistance?

  Temperature causes an increase in resistance
• Why does temperature increase resistance?

  More energy causes ions to vibrate more
• How do you determine resistance from an I-V graph?

  Resistance is the inverse of the gradient
• What would the I-V graph of a fixed resistor look like?

  A straight line through the origin
• What would the I-V graph of a filament lamp look like?

  A curve that flattens out at higher voltages
• What happens to the resistance of a filament lamp as temperature increases?

  Resistance increases due to more collisions
• What are the basic steps of the practical in Part B?

  1. Set up a circuit with two filament lamps in series
  2. Record potential difference and current values
  3. Set up a second circuit with lamps in parallel
  4. Compare the two arrangements
• What is the first step in the practical for Part B?

  Set up a circuit with two filament lamps in series
• What should you do after recording values for the series circuit?

  Set up a second circuit with lamps in parallel
• Which lamp arrangement has the greatest total resistance?

  Two lamps in series
• How does the total resistance of the parallel combination compare to individual resistances?

  Total resistance is smaller than the smallest individual resistance
• What safety precautions should be taken when using filament bulbs?

  • Avoid touching them when switched on
  • Do not use too high a voltage