P2

• What is the definition of current in electricity?

  Flow of electrical charge
• What is the unit of current?

  Ampere, A
• What is the definition of potential difference?

  Driving force that pushes charge round
• What is the unit of potential difference?

  Volt, V
• What is the definition of resistance?

  Anything that slows down charge flow
• What is the unit of resistance?

  Ohm, Ω
• What happens to current if there is no source of potential difference?

  No current flows
• What factors affect the current through a component?

  The component's resistance and the potential difference across it
• How does resistance affect current?

  The greater the resistance, the smaller the current
• How does potential difference affect current for a fixed resistance?

  The greater the potential difference, the larger the current
• What is the equation relating charge, current, and time?

  Q = It
• What does the symbol 'I' represent in the equation Q = It?

  Current (A)
• What does the symbol 'Q' represent in the equation Q = It?

  Charge flow (coulombs, C)
• What does the symbol 't' represent in the equation Q = It?

  Time (s)
• What is the potential difference equation?

  V = IR
• What does 'V' represent in the equation V = IR?

  Potential difference (V)
• What does 'I' represent in the equation V = IR?

  Current (A)
• What does 'R' represent in the equation V = IR?

  Resistance (Ω)
• What are the characteristics of an Ohmic conductor?

  • Current is directly proportional to potential difference
  • Resistance remains constant
  • Graph is linear
• What happens to the resistance of a filament lamp as the current increases?

  • Resistance increases
  • Temperature of filament increases
• What is the behavior of a diode in a circuit?

  • High resistance in one direction
  • Current only flows in the other direction
• How does resistance change in LDRs and thermistors?

  • LDR: Resistance decreases in brighter light
  • Thermistor: Resistance decreases in hotter temperatures
• What are the key features of series circuits?

  • Current is the same everywhere (I₁ = I₂)
  • Total potential difference is shared (V_Total = V₁ + V₂)
  • Total resistance is the sum of resistances (R_Total = R₁ + R₂)
• What are the key features of parallel circuits?

  • Total current is the sum of currents (I_Total = I₁ + I₂)
  • Potential difference across each branch is the same (V₁ = V₂ = V_Total)
  • Total resistance is less than the smallest resistor
• What type of current is produced by batteries?

  Direct current (dc)
• What type of current is used in mains supply?

  Alternating current (ac)
• What is the frequency of the UK mains supply?

  50 Hz
• What is the voltage of the UK mains supply?

  Around 230 V
• What are the functions of the three wires in a three-core cable?

  • Live wire: Provides alternating potential difference
  • Neutral wire: Completes the circuit
  • Earth wire: Stops appliance casing from becoming live
• What can cause electric shocks?

  Large potential difference across the body
• Why can electric shocks occur even when a plug socket is turned off?

  There is still danger of an electric shock
• What happens when charge flows in terms of energy transfer?

  • Work is done
  • Energy is transferred
• What is the equation for energy transferred electrically?

  E = QV
• What does 'E' represent in the equation E = QV?

  Energy transferred (J)
• What does 'Q' represent in the equation E = QV?

  Charge flow (C)
• What does 'V' represent in the equation E = QV?

  Potential difference (V)
• What is the definition of power in electricity?

  Energy transferred per second
• What is the equation for power?

  P = VI
• What does 'P' represent in the equation P = VI?

  Power (W)
• What does 'I' represent in the equation P = VI?

  Current (A)