Lec 2: The global energy budget Flashcards
The global energy budget
Define Energy. Name some different forms it can take and the units often used and what are the main 2 types of energy found in a substance?
Energy is the capacity to do work in the form of motion.
It’s a very loose definition that regroups all the different forms energy can take (i.e. Thermal, Radiant, Kinetic, Electrical, Chemical, etc).
Energy can be measured with a range of units ( Joules, Electron-Volts, KiloWatt-Hour, Cal, etc)
Energy exists in one of the 2 states in a substance
- Potential energy
- Kinetic energy
What is the difference between potential and kinetic energy? Name their respective equations.
Potential energy: PE = meh
Kinetic energy: K = 1/2mv^2
The difference is mainly that potential energy relates to an object that is still whereas kinetic refers to motion.
What does the acronym CAPE stand for? To which natural phenomenon is it linked?
CAPE = Convective Available Potential Energy
It is the capacity of the atmosphere to support the upward air movement involved in the formation of severe thunderstorms and even tornadoes
How do we measure the Kinetic energy of molecules? And what does that measure represent?
Temperature: the average speed of atoms or molecules in a substance
What is the absolute zero?
it is the theoretical point in temperature where molecules stop moving entirely (0 K, -273°C )
What are the 3 types of heat transfer
- Conduction
- Convection
- Radiation
what direction does heat move during heat transfer?
From the warmer object to the colder object
Define Conduction and its relation with temperature difference.
- Direct contact
- Thermal conductivity depends on the substance
- Metal is one of the best
- The greater the temperature difference, the faster the heat transfer
how do molecules interact during conduction? Like how does the heat transfer happen on a molecular level?
- Energy from the warmer substance causes molecules in the colder substance to vibrate faster
- as molecules vibrate faster, they cause adjacent molecules to vibrate faster, which can cause further adjacent molecules to vibrate faster
- Until the entire substance is vibrating faster
- as molecules vibrate faster, they cause adjacent molecules to vibrate faster, which can cause further adjacent molecules to vibrate faster
What is convection?
Transfer of heat through the mass movement of a liquid or a gas
A change in thermal energy can lead to a change in phase liquid to gas example: boiling water
What is the link between temperature and density?
- Temperature is related to density:
- Increase temperature → increase distance between molecules
What is radiation? What happens to the objects during radiation heat transfer?
- energy that is transmitted from one substance to another in the form of waves
- although these waves can act as a particle in some situations
- Energy is only acquired by an object when the waves are absorbed by an object
- energy is not released as the waves travel
- The substance that emits radiation loses energy, while the one that absorbs radiation gains energy
what separates radiation to conduction and convection
there is no need for contact between the substances since it is through electromagnetic waves that the transfer takes place ( no need for molecules to propagate)
What relation describes the Stefan-Boltzmann Law?
As the temperature of an object increases, more total radiation is emitted each second
What relation describes Wien’s law?
As the temperature of an object increases, the wavelength at which most of the energy is released will become shorter
