P1 Flashcards
What is the most important rule for energy?
Energy is never created or destroyed only transferred.
What are the 8 energy stores?
Thermal; kinetic; gravitational potential; elastic potential; chemical; magnetic; electrostatic; nuclear.
What are the 4 energy transfers?
Mechanical; electrical; heating; radiation (e.g. light or sound).
What is a system?
An object or group of objects.
What is a closed system?
No matter or energy can leave the system - energy change is always 0.
What does work done mean?
Energy is transferred.
What are the 2 types of work done?
Mechanical - applying a force. Electrical - current flows so it is the energy needed to overcome resistance.
How does energy change when an object is projected upwards?
Energy transfer from chemical store in person’s arm to kinetic store of ball and arm. Energy is mechanically transferred.
How does energy change when a moving object hits an obstacle?
Energy from the kinetic energy store in wheels transfers to thermal energy store of surroundings and maybe sound waves. Energy is transferred by heating and radiation.
How does energy change when an object accelerates by a constant force e.g. a ball falling?
Energy is transferred from the gravitational potential energy store in the object to the kinetic energy store. Energy is transferred mechanically.
How does energy change when a vehicle slows down?
Energy is transferred from the kinetic energy store of the vehicle to the thermal energy store of the surroundings. Energy is transferred by heating.
How does energy change when bringing water to a boil in an electric kettle?
Energy from the chemical store of the cable is transferred electrically to the thermal energy store of the kettle heating element. The thermal energy is then transferred to the thermal energy of the water by heating.
Name the names and units for Ek = 0.5 m v²
Kinetic energy in joules. Mass in kilograms. Speed in m/s
Name the names and units for Ee = 0.5 k e²
Elastic potential energy in joules. Spring constant in N/m. Extension in meters.
Name the names and units for Ep =m g h
Gravitational potential energy in joules. Mass in kilograms. Gravitational field strength in N/Kg. Height in meters.
Name the names and units for ∆E =m c ∆θ
Change in thermal energy in joules. Mass in kilograms. Specific heat capacity in J/kg °C. Temperature change in °C.
Required practical activity 1: investigation to determine the specific heat capacity of one or more materials.
- Have a block of material (e.g. copper) with 2 holes in it for the thermometer and heater. 2. Measure the mass and add an insulating layer to reduce energy transferred to the surroundings. 3. Measure initial temperature and set pd to 10V and start a stopwatch. Current from powerpack transfers energy electrically from power supply to thermal energy store of heater. Then it transfers to thermal energy store of material by heating. 4. Take readings of temperature every 10 mins about 10 times. 5. Turn off power supply and work out energy using E=PT and then ∆E =m c ∆θ. 6. You can repeat with different materials to compare.
Name the names and units for P = E / t
Power in watts. Energy transferred in joules. Time in seconds.
How can you illustrate the definition of power.
2 racecars have the same length of track but one finishes faster as they have more power in their energy so have transferred energy in less time.
What is dissipated energy?
Wasted energy because the energy is being stored in a way that is not useful.
How can you reduce unwanted energy transfers? (2)
- Lubricants - they reduce friction so less force against the objects. 2. Insultation.
How is a house insulated? (4)
- Cavity walls insulation - air gap filled with foam which reduces energy transfer. 2. Loft insulation. 3. Double glazed windows - air gap which reduces energy transfer. 4. Draught excluders around doors and windows.
What is conduction?
The process where vibrating particles transfer energy to neighbouring particles.
Where can conduction happen?
Solids
If you have a high thermal conductivity of a material is there more conduction or less?
The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.
What actually happens in conduction?
The particles being heated vibrate and collide more. This causes energy to be transferred into the kinetic store. This continues until all the energy has been transferred to the thermal energy store (by heating).
What is convection?
Where energetic particles move away from hotter to cooler regions.
Where can convection happen?
Gases and liquids.
How is a convection current created?
Warm and less dense air will rise above the denser, cooler air. There must be a constant heat source.
What actually is convection?
Energy is transferred to the thermal energy store by heating. Particles move faster so the region being heated becomes less dense.
If you have thicker walls in your house what does it mean for thermal conductivity?
Lower thermal conductivity - slower rate of energy transfer so will not lose heat.
Required practical activity 2 (physics only): investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material.
- Boil water in a kettle and pour into a beaker with a lid. 2. Measure the mass of water and using a thermometer measure the initial temperature. 3. Seal it and leave for 5 mins (with a stopwatch). 4. Measure final temperature and pour the water out and leave the container to cool. 5. Repeat with different materials.
What are the main non - renewable energy resources available for use on Earth?
Fossil fuels - coal and gas and oil.
Efficiency equation
efficiency = useful output energy / total input energy
What are the main renewable energy resources available for use on Earth?
- Solar. 2. Wind. 3. Water waves. 4. Hydroelectricity. 5. Bio-fuel. 6. Tides. 7. Geothermal. 8. Nuclear
What is the definition of renewable?
A renewable energy resource is one that is being (or can be) replenished as it is used.
What are uses of energy resources? (3)
- Transport. 2. Electricity. 3. Heating.
