current potential difference and resistance

• What are the building blocks of all matter?

  Atoms
• How many atoms could fit across a thumbnail?

  About one hundred million
• What orbits around the nucleus of an atom?

  Electrons
• What makes up the nucleus of an atom?

  Protons and neutrons
• How much smaller is the radius of the nucleus compared to the whole atom?

  Over 10,000 times smaller
• What does the nucleus contain in terms of mass?

  Almost all of the mass of the atom
• What are the parts of an atom?

  • Nucleus
  • Protons: positively charged, mass of 1 unit
  • Neutrons: no charge, mass of 1 unit
  • Electrons: negative charge, mass of 1/2000 unit
• What is the Plum Pudding Model?


  A model of the atom to avoid in exams
• What are the functions of common circuit components?

  • Cell/Battery: Provides potential difference
  • Switch: Turns circuit on/off
  • Fixed Resistor: Limits current flow
  • Variable Resistor: Changes resistance
  • Thermistor: Resistance changes with temperature
  • LDR: Resistance changes with light intensity
  • Motor: Converts electrical to mechanical energy
  • Diode: Allows current in one direction
  • LED: Emits light when current flows
  • Ammeter: Measures current in series
  • Voltmeter: Measures potential difference in parallel
• What does a cell or battery provide in a circuit?

  A source of potential difference
• What does a switch do in a circuit?

  Turns the circuit on or off
• What is the role of a fixed resistor?

  Limits the flow of current
• How does a variable resistor work?

  Changes resistance with a slider
• What happens to a thermistor's resistance as temperature increases?

  Resistance decreases
• What does an LDR's resistance depend on?

  Light intensity
• What does a motor do in a circuit?

  Converts electrical energy to mechanical energy
• What is the function of a diode?

  Allows current to flow in one direction
• What does an LED do?

  Emits light when current passes
• How is current measured in a circuit?

  Using an ammeter
• How is a voltmeter connected in a circuit?

  In parallel with the component
• What are the key rules for drawing circuit diagrams?

  • Include an energy source
  • Ensure a closed path for current
  • Use correct circuit symbols
  • Ammeter in series, voltmeter in parallel
  • Current flows from positive to negative
• What is potential difference also known as?

  Voltage
• What is potential difference defined as?

  Energy transferred per unit charge
• What is the unit of potential difference?

  Volt (V)
• How can potential difference be calculated?

  Using the formula $V =$$\frac{E}{Q}$
• What does a voltmeter measure?

  Potential difference across a component
• What is the relationship between current, charge, and time?

  Current is charge per second
• What is the unit of current?

  Amperes (A)
• What is the flow of current in metal wires?

  A flow of electrons
• What is the definition of electric current?

  Rate of flow of charge
• When will 8 mA of current pass through a circuit?

  When 4 C passes in 500 s
• How is current measured in a circuit?

  Using an ammeter in series
• What must a circuit include for current to flow?

  A source of potential difference
• What happens to current in a closed-loop circuit?

  Current is the same at any point
• What happens at a junction in a circuit?

  Current flowing in equals current flowing out
• What is conventional current?

  Flow of positive charge from positive to negative
• How is current conserved at a junction?

  Current in equals current out
• What is the relationship between resistance and current?

  Higher resistance means lower current
• What are the two types of resistors?

  Fixed and variable resistors
• How does the length of wire affect resistance?

  Longer wire has more resistance