Investigating Resistance

• What is the focus of the practical described in the video?

  Factors affecting the resistance of electrical circuits
• What percentage of exam marks come from required practicals?

  At least 15%
• What equipment is used in the resistance practical?

  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 do you calculate resistance in the circuit?

  Resistance = Potential difference / Current
• What factor are we investigating that affects resistance?

  Length of the wire
• How do you increase the length of the wire in the experiment?

  Move the crocodile clips further apart
• What does a straight line graph through zero indicate?

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

  Reading when the value should be zero
• How does a zero error affect resistance measurements?

  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?

  Increases resistance as temperature rises
• What can be done to reduce heating effects in the wire?

  Use low potential difference and turn off current
• What is a variable resistor used for?

  To control potential difference across a load
• How does a variable resistor change resistance?

  By changing the length of wire in a coil
• What happens to a lamp when resistance is increased?

  The lamp becomes dimmer
• What are the key steps in investigating resistance in a circuit?

  1. Set up the circuit with battery, ammeter, voltmeter, and wire.
  2. Measure current and potential difference.
  3. Calculate resistance using the formula.
  4. Change the length of the wire using crocodile clips.
  5. Record and analyze results to observe the relationship.
• What are the main issues to consider in the resistance practical?

  • Zero error: systematic error requiring subtraction from readings
  • Heating effects: increased temperature raises resistance
  • Use low potential difference and turn off current between readings to minimize errors