Physics2

• From where is heat transferred?

  From a hotter object to a cooler object
• What are the three ways heat can be transferred?

  Conduction, convection, and radiation
• How does conduction occur?

  Particles gain thermal energy and vibrate faster
• Why are metals good conductors of heat?

  They contain delocalised electrons
• What is thermal conductivity?

  Measure of heat transfer speed through a substance
• What materials are excellent heat insulators?

  Low thermal conductivity materials
• Which state of matter is the best conductor of heat?

  Solids
• Why are frying pans made of high thermal conductivity materials?

  To transfer heat quickly from flame to food
• How do insulation materials work?

  They trap air, slowing heat loss
• Why are fossil fuels considered finite resources?

  They take millions of years to form
• What is a key feature of a coal power station?

  It burns coal to generate electricity
• What is a significant difference in energy transfer in a nuclear power station?

  No burning of fuel occurs
• What are the advantages of fossil fuels?

  Cheap, accessible, and reliable fuel
• What are the disadvantages of nuclear energy?

  Expensive, radioactive waste, and explosion risk
• Which fossil fuel is the most polluting?

  Coal
• When is electricity demand highest during the day?

  At 8pm when people use appliances
• What does voltage represent in a circuit?

  The push force that drives current
• What causes resistance in a circuit?

  Electrons collide with metal ions in the wire
• What is needed for an electrical circuit to work?

  A source of potential difference and a complete circuit
• How does the length of a wire affect resistance?

  Longer wires increase resistance
• How does the diameter of a wire affect resistance?

  Larger diameter wires have lower resistance
• What are the characteristics of series and parallel circuits?

  Series Circuit:

  • One loop, one path for current
  • Current is the same everywhere
  • Voltage adds up across components
  • Net resistance increases with more components

  
  

  Parallel Circuit:

  • Multiple paths for current
  • Current splits at branches
  • Each branch gets full voltage
  • Net resistance decreases with more loops
• How do you calculate net resistance in a series circuit?

  Sum of the resistance of components
• How do you calculate net resistance using Ohm's law?

  Use V/I = R
• What is an LDR?

  A variable resistor that changes with light intensity
• What is a thermistor?

  A variable resistor that changes with temperature
• What is direct current (DC)?

  Current that travels in one direction
• What is alternating current (AC)?

  Current that changes direction continuously
• How do you calculate frequency from an oscilloscope trace?

  Frequency = 1/time period
• What voltage and frequency does the UK mains power supply provide?

  230V and 50Hz
• What is the National Grid and its components?

  • Power stations
  • Substations
  • Transformers
  • Wires
  • Pylons
• What is the purpose of step-up transformers?

  To increase voltage and decrease current
• How does the Earth wire protect users from electric shock?

  Provides an alternative pathway for current
• What happens if the live wire touches the metal casing?

  Current travels through the user into the ground
• Why do substances in different states have different densities?

  Particles are arranged differently in each state
• What is density?

  Mass per unit volume
• What is unique about water's density?

  Ice is less dense than liquid water
• How do you measure the density of a regular solid?

  Mass divided by volume
• How do you measure the density of an irregular solid?

  Use water displacement method
• How do you measure the density of a liquid?

  Mass divided by volume