Required Practical 3: Resistance

• What should you be able to describe by the end of the video?

  Factors affecting the resistance of circuits
• Why is it important to learn about required practicals?

  They account for at least 15% of exam marks
• What factors are being investigated in the practical?

  • Resistance of electrical circuits
  • Focus on the length of a wire
• What equipment is used in the practical investigation?

  Battery, ammeter, voltmeter, wire
• What does the ammeter measure in the circuit?

  Current in the circuit
• What does the voltmeter measure in the circuit?

  Potential difference across the wire
• How is resistance calculated in the circuit?

  Resistance = potential difference / current
• What is the relationship between resistance and the length of the wire?

  Resistance is directly proportional to length
• How can the length of the wire be increased in the experiment?

  By moving the crocodile clips apart
• What does a straight line graph through zero indicate?

  Resistance is directly proportional to length
• What is a zero error in this context?

  A reading when the value should be zero
• How does zero error affect resistance readings?

  It requires subtraction from all readings
• What causes zero error in this experiment?

  Equipment and contact resistance issues
• How does heating affect resistance in the wire?

  Increased temperature raises resistance
• What can be done to reduce heating effects in the wire?

  Use low potential difference and turn off current
• How does a variable resistor work?

  • Contains a long piece of wire in a coil
  • Slider changes the length of wire in the circuit
  • Controls potential difference across the load
• What happens to the lamp when resistance is increased using a variable resistor?

  The lamp becomes dimmer
• Where can you find more questions on required practicals?

  In the vision workbook
• What is the main focus of the practical discussed in the video?

  Investigating resistance in electrical circuits