Energy, Heat & Albedo PDF document Week 4

In physics, energy is defined as

Capacity to do work or the ability
to move something
➢ Ability to change

Types of Energy

1. Kinetic (movement)
• the energy of movement
• mechanical energy that a body has by
virtue of its movement or motion
• results in work
2. Potential (stored)
• stored energy in an object due to its
position or configuration ~ energy at rest
• the potential for an object to do work;
available energy to do work
• energy before movement, waiting to
become kinetic
• e.g. chemical energy

Forms of Energy

− heat / thermal
− radiant (light, UV, IR...)
− electrical
− mechanical
− gravitational
− chemical (e.g. sugar )
− nuclear
− sound

What is Thermodynamics

➢ the study of energy transformations
➢ describe the behavior of energy in the universe

1st : Law of Conservation of Energy

First Law of Thermodynamics
➢ Energy cannot be created or destroyed
➢ Energy can change form
➢ Conservation of Energy

2nd : Law of Entropy

Second Law of Thermodynamics
▪ deals with the efficiency of energy transformations
▪ no energy conversion or transformation is 100% efficient;
at every conversion, some energy is lost as heat, which is
unavailable to do work
▪ heat increases the motion of molecules and therefore increases
their disorder. Entropy – another term for disorder
▪ systems, without continuous inputs of energy will eventually
become completely disordered

There are different wavelengths of radiation:

ultraviolet, visible light,
infrared

Light is a form of

electromagnetic
radiation

Light energy travels to earth in particles called photons. Photons ARE ..

discrete packets of light energy. Each photon has a specific wavelength and amount of energy.

Albedo = reflectivity

Snow: high albedo
NYC streets: low albedo

4 modes of heat transfer

Radiation
▪ Conduction
▪ Convection
▪ Evaporative cooling

Urban Heat Island Effect

occurs when cities and built-up metropolitan areas experience significantly warmer temperatures than surrounding rural landscapes.