Energy Transfers Flashcards
What are the 4 ways that energy can be transferred by heat
Evaporation
Conduction
Convection
Radiation
Explain the process of evaporation
It can take place from a liquid at any temperature. When a part of a liquid evaporates, it is the fastest moving particles that escape to form gas. The particles that are left are storing less energy as movement and so the temperature of the remaining liquid is lower
Explain the process of conduction
It takes place in solids and can also happen in liquids (although in liquids but not very well) . The particles in a solid are held together tightly. When they gain energy they vibrate faster and further and the vibrations are passed. Metals are the best conductors. Most other solids are poor conductors.
Why is conduction not so good in liquid
Particles are not as close in a liquid, so conduction is not very good. Particles in gases are a long way alert so gases hardly conduct heat at all.
Explain the process of convection
Takes place in fluids, whe part of a fluid is heated the particles spread further apart and the fluid becomes less dense. This makes it raise. As it rises it meets cooler fluids and passes the energy on. More cool fluid moves in to replace the rising fluid, setting up a convection current
Explain the process of infrared radiation
Can transfer energy through empty space and also through transparent materials. Radiation does not require the movement of particles. Any hot or warm, object gives off or emits radiation. When something takes in energy from radiation it is said to absorb
What is the definition of power
Power is the rate at which energy is transferred
What is power measured in
Watts or kilowatts
One watt is one joule of energy being transferred each second.
What is efficiency
Not all energy is transferred usefully, wasted energy is often transferred by heating. The percentage of useful energy produced is known as efficiency
What is the equation for working out efficiency
Useful energy transferred
Efficiency= ———————— X100%
Total energy supplied
What is internal energy/ thermal energy?
Measured in joules
The amount of thermal energy stored in something depends on how hot it is
The material it’s made from
It’s mass
What is the sankey diagram
sankey diagrams shows energy transfers, the width of each arrow shows the amount of energy it represents
What units of measurements do electricity companies use when measuring energy?
Kilowatts
How can we reduce our electricity bills?
We can insulate our homes and and use more efficient appliances
What is payback time?
The payback time of installing something that makes a home more energy efficient is the time taken for the cost of installation to be matched with the money saved.
