topic 10: electricity and circuits

• What is the charge of the nucleus in an atom?

  Positively charged
• What are the three subatomic particles of an atom?

  Proton, neutron, electron
• What is the relative mass of a proton?

  1
• What is the relative charge of a neutron?

  0
• What is the relative mass of an electron?

  0 (0.0005)
• What is the charge of an electron?

  • -1
• What are the characteristics of series circuits?

  • Closed circuit
  • Current is the same everywhere
  • Potential difference is shared across the whole circuit
  • Total resistance is the sum of the resistance in each component
• What are the characteristics of parallel circuits?

  • Branched circuit
  • Current splits into multiple paths
  • Voltage is the same across each branch
  • Total current into a junction equals total current in each branch
• What is potential difference represented by?

  'V'
• In what unit is potential difference measured?

  Volts
• What does potential difference measure?

  Energy transferred per unit charge
• How is potential difference measured?

  With a voltmeter, placed in parallel across a component
• When does current flow in a circuit?

  When there is a potential difference in a closed circuit
• What is the formula for energy transferred?

  $E =$$QV$
• What does a voltmeter measure?

  Potential difference
• What does an ammeter measure?

  Current
• What is the unit of current?

  Amps
• What is the relationship between potential difference, current, and resistance?

  $V =$$IR$
• How does resistance affect current flow?

  Greater resistance means smaller current
• What are the characteristics of series circuits regarding current and resistance?

  • Current is the same through all components
  • Total resistance is the sum of individual resistances
  • Can only switch all components off at once
• What are the characteristics of parallel circuits regarding current and resistance?

  • Current is shared between branches
  • Total resistance is less than the smallest branch
  • Each component can be switched off individually
• How does resistance change with current?

  Resistance increases as current increases
• How does resistance change with temperature?

  Resistance increases with temperature in normal wires
• How does resistance change with length of a wire?

  Greater length results in greater resistance
• How does cross-sectional area affect resistance?

  Thinner wires give greater resistance
• How does light intensity affect an LDR?

  Greater light intensity results in lower resistance
• How does voltage affect a diode?

  Diode allows current to flow in one direction only
• What is the efficiency of low resistance wires?

  Less energy loss as current flows through the circuit
• What are the steps for testing relationships in electrical components?

  1. Ensure components do not overheat
  2. Vary wire resistance and measure current
  3. Plot graphs to show relationships
• What is the formula for power in terms of energy transferred?

  $P =$$\frac{E}{t}$
• How is power related to current and voltage?

  $P =$$IV$
• What is the relationship between power and resistance?

  $P =$$I^2R$
• How is energy transferred from batteries to devices?

  From chemical potential to electrical energy to useful energy
• What is AC?

  Alternating current
• What is DC?

  Direct current
• What is the mains supply frequency in the UK?

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

  230V
• What are the functions of the three wires in a plug?

  • Live wire: carries voltage from mains to appliance
  • Neutral wire: completes the circuit
  • Earth wire: safety wire to prevent electric shock
• What happens if the live wire touches the metal casing of an appliance?

  The appliance becomes live, posing an electric shock risk
• What is the purpose of a fuse?

  To break the circuit if a large current passes through