Physics - Topic 10 - Electricity and Circuits

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

  Positively charged
• What surrounds the nucleus of an atom?

  Negatively charged electrons
• What are the relative masses and charges of protons, neutrons, and electrons?

  • Proton: Mass = 1, Charge = +1
  • Neutron: Mass = 1, Charge = 0
  • Electron: Mass = 0 (0.0005), Charge = -1
• What is the unit of potential difference?

  Volts
• What does potential difference represent?

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

  With a voltmeter placed in parallel across a component
• What happens when there is a potential difference in a closed circuit?

  Current will always flow
• What is the formula for energy transferred?

  $E =$$QV$
• What is the symbol for current?

  I
• How is current measured?

  In amps
• What does the equation $V =$$IR$ represent?


  Potential difference equals current times resistance
• What are the characteristics of series circuits?

  • Components are connected end to end
  • Current is the same through all components
  • Potential difference is shared across the circuit
  • Total resistance is the sum of individual resistances
• What are the characteristics of parallel circuits?

  • Components are connected separately to the power supply
  • Current flows through each component separately
  • Potential difference is the same across all branches
  • Total resistance is less than the smallest branch resistance
• How does resistance change with current?

  Resistance increases as current increases due to electron collisions
• How does temperature affect resistance in normal wires?

  Resistance increases as temperature increases
• What happens to the resistance of a thermistor as temperature increases?

  Resistance decreases
• How does the length of a wire affect its resistance?

  Greater length increases resistance
• How does the cross-sectional area of a wire affect its resistance?

  Thinner wires have greater resistance
• How does light intensity affect the resistance of an LDR?

  Greater light intensity decreases resistance
• What is the behavior of a diode in terms of current flow?

  Allows current to flow freely in one direction
• What is the relationship between power, current, and potential difference?

  • Power is energy transferred per second
  • $P =$$IV$
  • Doubling current doubles power
  • Power loss is proportional to resistance and current squared
• What is the unit of power?

  Watts
• What is the mains supply frequency in the UK?

  50Hz
• What color is the live wire in a plug?

  Brown
• What is the purpose of the earth wire?

  To prevent the appliance from becoming live
• What happens if the live wire touches the metal casing of an appliance?

  The casing becomes live, posing an electric shock risk
• What does a fuse do in a circuit?

  Melts to break the circuit if a large current passes through
• What is power rating in appliances?

  • Power rating indicates energy consumption per second
  • Greater power rating means greater energy consumption