♡ Topic 10_Electricity and circuits ♡

• Three subatomic components of an atom:

  • Electrons
  • Protons
  • Neutrons
• Structure of an atom:

  • Neutrons and protons in the nucleus
  • Electrons surrounding the nucleus in shells
• Charged particles in an atom:

  • Proton (+1)
  • Electron (-1)
• In a closed circuit with a potential difference, there will also be current
• Current is defined as the rate of flow of charge (or electrons) around a circuit
• Units of charge: Coulombs, C
• Circuit symbol for a switch:

  • Closed
  • Open
• Circuit symbol for a cell:

  • Positive (+)
  • Negative (-)
• Circuit symbol for a battery:

  • Positive (+)
  • Negative (-)
  • Positive (+)
  • Negative (-)
• Circuit symbol for a lamp
• Circuit symbol for a fuse
• Circuit symbol for a voltmeter: V
• Circuit symbol for an ammeter: A
• Circuit symbol for a diode
• Circuit symbol for a resistor
• Circuit symbol for a thermistor
• Circuit symbol for a variable resistor
• Circuit symbol for an LDR
• Circuit symbol for an LED
• Factors affecting the energy transferred when charge flows through a component:

  • Amount of charge
  • Potential difference across the component
• Equation linking energy, current, and potential difference with all SI units:

  Energy (J) = Potential difference (V) x Current (A) x Time (s)

  E = VIt
• Potential difference defined in terms of charge:

  The work done per unit charge
• Equation relating potential difference to charge:

  Energy transferred (J) = Charge (C) x Potential difference (V)

  E = QV
• Reason why an electrical current flowing through a resistor heats it up:

  Collisions between electrons and ions in the resistor's lattice cause a transfer of kinetic energy into thermal energy, released into the surroundings
• How low resistance wires reduce unwanted energy transfers:

  Less resistance leads to fewer collisions, reducing wasted energy through heating
• Advantages of the heating effect:

  Useful for appliances like toasters or electrical fires where heat is desired
• Advantages and disadvantages of the heating effect:

  • Loss of energy as heat can make an appliance inefficient
  • Risk of fire or device damage if appliance overheats
• Energy transferred per second is also known as:

  Power
• Definition of power:

  Rate of energy transfer or the rate at which work is done
• Units of power:

  Watts, W
• Equation linking power and potential difference with all SI units:

  Power (W) = Current (A) x Potential difference (V)

  P = IV
• Equation to calculate power without potential difference with all SI units:

  Power (W) = Current² (A) x Resistance (Ω)

  P = I²R
• Equation linking power and energy with all SI units:

  Power (W) = Energy (J) ÷ Time (s)

  P = E/t
• Equations linking power and resistance with all SI units:

  Power (W) = Current² (A) x Resistance (Ω)

  P = I² x R

  Power (W) = Potential difference² (V) ÷ Resistance (Ω)

  P = V² ÷ R
• AC stands for Alternating Current, which constantly changes between a negative and a positive maximum
• DC stands for Direct Current, which takes a constant value
• Mains electricity is an AC supply, with AC standing for Alternating Current
• The frequency of a supply refers to the rate at which an AC current changes
• The frequency and voltage of the UK mains electricity supply are:

  • Frequency: 50 Hz
  • Voltage: 230V
• Batteries and cells supply Direct Current (DC)