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: Relative Mass = 1, Relative Charge = +1
  • Neutron: Relative Mass = 1, Relative Charge = 0
  • Electron: Relative Mass = 0 (0.0005), Relative 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

  
• When will current flow in a circuit?

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

  $E =$$QV$
• What does 'I' represent in electrical terms?

  Current
• How is current measured?


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

  $V =$$IR$
• What happens to current when resistance increases?

  Current decreases
• 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 branch with the smallest resistance
• How does resistance change with length of a wire?

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

  Thinner wires have greater resistance
• What happens to resistance in a thermistor as temperature increases?

  Resistance decreases
• How does light intensity affect an LDR's resistance?

  Greater light intensity results in lower resistance
• What is the formula for power in an electrical circuit?

  $P =$$IV$
• How is power loss related to resistance and current?

  Power loss is proportional to resistance and current squared
• What is the frequency and voltage of the mains supply in the UK?

  50Hz and 230V
• What are the functions of the wires in a plug?

  • Live wire (brown): carries voltage from mains to appliance
  • Neutral wire (blue): completes the circuit
  • Earth wire (green/yellow): safety wire to prevent electric shock
• What is the purpose of a fuse in a plug?

  To break the circuit if a large current passes through
• What does a greater power rating indicate about an appliance?

  Greater energy consumption per second
• What is the relationship between energy, current, potential difference, and time?

  • Energy transferred (joule, J) = current (ampere, A) × potential difference (volt, V) × time (second, s)
  • Formula: $E =$$IVt$
• What is the relationship between power, current, and voltage?

  • Power is directly proportional to current and voltage
  • Doubling current doubles power
  • Formula: $P =$$IV$
• What is the formula for electrical power in terms of resistance?

  • Electrical power (watt, W) = current squared (ampere², A²) × resistance (ohm, Ω)
  • Formula: $P =$$I^2R$