P2- Electricity

• What must be true for electrical charge to flow in a circuit?

  The circuit must be closed and there must be a source of potential difference.
• What is electrical current?

  Current is the flow of electrical charge.
• How does the rate of flow of charge relate to current?

  The greater the rate of flow of charge, the greater the current.
• What is the formula relating charge flow, current, and time?

  $Q =$$I \cdot t$
• What is true about current in a single closed loop?

  The current has the same value at any point in the loop.
• What factors affect the current through a component?

  The current depends on both the resistance of the component and the potential difference across it.
• How does resistance affect current for a given potential difference?

  The greater the resistance, the smaller the current for a given potential difference.
• What is the equation that relates potential difference, current, and resistance?

  $V =$$I \cdot R$
• What characterizes an ohmic conductor?

  If the resistance is constant, current is directly proportional to the potential difference, resulting in a linear graph.
• How does the resistance of components like lamps and diodes change with current?

  The resistance changes with the current, resulting in a nonlinear graph.

  
• How does temperature affect the resistance of a thermistor?

  In hotter temperatures, the resistance of a thermistor is lower.
• How does the length of a wire affect its resistance?

  The greater the length of the wire, the more resistance and the lower the current.
• What happens to the resistance of an LDR in bright light?

  The greater the intensity of light, the lower the resistance of an LDR.
• What is the function of a diode in a circuit?

  A diode allows current to flow freely in one direction and has a very high resistance in the opposite direction.
• What does a sharper gradient on a resistance graph indicate?

  A sharper gradient indicates a lower resistance.
• What are the characteristics of series circuits?

  • Closed circuit
  • Current follows a single path
  • Current is the same everywhere
  • Total Resistance = \( R_1 + R_2 + \ldots \)
• What are the characteristics of parallel circuits?

  • Branched circuit
  • Current splits into multiple paths
  • Total current into a junction = total current in each branch
  • Potential difference is the same across each branch
• How is potential difference shared in a series circuit?

  The potential difference of the power supply is the sum of the potential differences across each component.
• How is current shared in a parallel circuit?

  The current through the source is the sum of the current through each branch.
• What is the frequency and voltage of mains electricity in the UK?

  The frequency is 50 Hz and the voltage is about 230 V.
• What is the difference between AC and DC current?

  AC is alternating current that varies continuously, while DC is direct current that moves in one direction only.
• What are the three wires in a plug and their functions?

  Live wire (brown), neutral wire (blue), and earth wire (green/yellow).
• What is the purpose of the earth wire in a plug?

  The earth wire is a safety wire that prevents the appliance from becoming live in case of a fault.
• How is power defined in electrical terms?

  Power is the energy transferred per second and is directly proportional to current and voltage.
• What is the formula for energy transferred in terms of power and time?

  $E =$$P \cdot t$
• What is the formula for energy transferred in terms of charge and potential difference?

  $E =$$Q \cdot V$
• What is the National Grid and its function?

  • A system of cables and transformers linking power stations to consumers
  • Transfers electrical power from power stations to consumers
• What is the role of step-up transformers in the National Grid?

  Step-up transformers increase the potential difference from the power station to the National Grid.
• What is the role of step-down transformers in the National Grid?

  Step-down transformers decrease the potential difference from the National Grid to consumers for safety.
• What is charge in terms of electrical properties?

  Charge is a property of all matter, with positive and negative charges existing.
• What happens when two insulators are rubbed together?

  Electrons are transferred from one object to the other, forming a positive charge on one and a negative charge on the other.
• What causes sparking in static electricity?

  Sparking occurs when enough charge builds up and the objects are close but not touching, causing charge to jump through the air.
• What is electrostatic force?

  Electrostatic force is the force of attraction or repulsion experienced by charged objects.
• How does the distance between charged objects affect the electrostatic force?

  The closer the objects are, the greater the force, which is proportional to the inverse square of the distance.
• What are the differences between conductors and insulators?

  • Insulators: Electrons cannot flow, fixed electrons
  • Conductors: Electrons can flow, delocalised electrons