• Energy Update!• Homework Assignment Help

• Review Last Lecture• Energy and Society

• Today’s Material:• Energy• Heat

• Heat Activity (Probably Next Monday)• Homework 2: Wed 9/10/14

• Chapter 3 Exercises 1, 2, 5, 6, 9, 10

Renewable energy capacity grows at fastest ever paceGreen technologies now produce 22% of world's electricity

http://www.theguardian.com/environment/2014/aug/28/renewable-energy-capacity-grows-fastest-ever-pace?CMP=twt_gu

More than $250bn (£150bn) was invested in "green" generating systems in 2013, although the speed of growth is expected to slacken, partly because politicians are becoming nervous about the cost of subsidies.

The current growth rate for installing new windfarms and solar arrays is impressive but the IEA believes it is not enough to meet climate change targets, triggering calls in Brussels from green power lobby groups for Europe to adopt tougher, binding targets.

Wind turbines in China.

We Are On The Verge Of An Electric Car Battery Breakthrough

Electric vehicles are cool. They’re inexpensive to operate, can make our air cleaner, and help reduce the amount of climate change-causing gases released into the atmosphere. But right now, they’re also mostly just for rich people. The initial cost of buying the car, combined with their limited availability, is just too much for most people to justify making the switch.That could soon change, though, because investment pundits think that Tesla Motors is on the verge of achieving something big: A battery cheap enough to make electric vehicles cost-competitive with conventional cars. Daniel Sparks at Motley Fool is reporting that the company is on the right track towards developing a battery that costs only $100 per kilowatt-hour — a cost widely believed to be the threshold where electric vehicles can finally be cost-competitive.

HOMEWORK ASSISTANCECH 1: 1CH 2: 1, 3, 4, 5

The sun’s electromagnetic spectrum and some of the descriptive names of each region. The numbers underneath the curve approximate the percent of energy the sun radiates in various regions.

0.4 μm = 400 nm 0.7 μm = 700 nm

The hotter sun not only radiates more energy than that of the cooler earth (the area under the curve), but it also radiates the majority of its energy at much shorter wavelengths. (The area under the curves is equal to the total energy emitted, and the scales for the two curves differ by a factor of 100,000.)

Potential and kinetic energy. (a) Gravitational potential energy of the skier becomes kinetic energy as she heads down the slope. (b) Elastic potential energy stored in the bow becomes kinetic energy of the arrow.

Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less intense) to a surface than direct sun rays.

End-use energy consumption, by sector, for three countries in the early twenty-first century.

Why do these countries have a different breakdown of energy uses?Japan is a compact industrialized country, with a well developed rail system, so uses a greater fraction of its energy for industry than does the USA.

Ghana is a typical developing country and has much smaller industrial and commercial sectors, so devotes most of its limited energy to residential uses.

Energy consumption by sector for the United States, (a) with end-use accounting and (b) accounting for primary energy. End-use energy is measured by the amounts of energy that actually reach the end user. Primary energy is the fuel energy that goes into the production of energy (i.e. the energy that originally goes into the power plant).

Why are these percentages different?

TODAY’S MATERIAL

Force can be thought of as a push or pull upon an object.

http://image.tutorvista.com/content/feed/tvcs/push20and20pull.JPG

http://www.bbc.co.uk/bitesize/standard/physics/images/tug_of_war.gif

http://www.bbc.co.uk/bitesize/standard/physics/images/trolley.gif

When forces are balanced, there is no acceleration.

When forces are unbalanced, there is acceleration.

Force = Mass X Acceleration

The 3 fundamental forces: (a) Gravity governs the large-scale structure of the universe. It holds you to Earth and keeps a satellite in orbit. Gravitational potential energy is the energy source for hydroelectric power plants. (b) The electromagnetic force is responsible for the structure of matter at the molecular level; the associated potential energy is released in chemical reactions such as those that occur in burning fuels. Electromagnetism is also involved in the production and transmission of electrical energy. (c) The nuclear force binds protons and neutrons to make atomic nuclei. The associated potential energy is the energy source for nuclear power plants.

Chemical reactions in a battery separate positive and negative charge. Connecting an external circuit, such as the lamp shown here, allows the battery to deliver electrical energy as charge flows through the circuit.

(a) A simple electric generator consists of a single wire loop rotating between the poles of a magnet. The stationary brushes allow current to flow from the rotating contacts to the external circuit. A practical generator has many loops, each with many turns of wire. (b) This large generator produces 650 MW of electric power.

The electromagnetic spectrum. Electromagnetic waves are characterized by their frequency in hertz (wave cycles per second) or their wavelength in meters (the distance between wave crests). The two are inversely related. Note the highly nonlinear scale, with each tick mark representing a factor of 1,000 increase or decrease in frequency or wavelength. The Sun’s energy output is mostly in the visible and adjacent infrared portion of the spectrum, with a little ultraviolet.

ƛ = c/FWavelength = wave speed/frequency

E = hf = hc/ ƛ

Quantifying Energy

1 Joule = 1 Watt Second

Lift a 2 pund book 4 inches, you will have expended about 1 Joule of energy

1 Calorie = the amount of energy it takes to raise the temperature or 1 gram of water by 1 degree Celsius

1 British Thermal Unit (BTU) = the amount of energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit

Table 3.1 shows some energy and power units.

Force and work. (a) When you lift a bowling ball, you apply a force in the direction of its motion. You do work on the ball, in this case increasing its gravitational potential energy. (b) When you carry the ball horizontally, you apply a force to counter its weight, but you don’t do work on the ball because the force is at right angles to its motion. (c) When you apply an upward force to stop a falling ball, the force is opposite the ball’s motion, so here you do negative work that reduces the ball’s kinetic energy.

Work = Force X Distance

Rising out of a knee bend requires that I apply a 600-N force over a distance of 0.17 m, resulting in 100 J of work done. Repeating once per second gives a power output of 100 W.

Work = mass X gravity X height

Class Review:Energy Update!EnergyWork

Next ClassHeatHeatflow

Kinetic energy increases with the square of the speed. Shown here is kinetic energy versus speed for a Honda Civic compact car (empty weight 1,268 kg) and a Ford Excursion SUV (empty weight 3,129 kg), each with a 68-kg driver. The weight difference accounts for much of the difference in fuel efficiency between these vehicles.

Temperature measures the average molecular kinetic energy. At lower temperatures, the molecules of a gas have lower kinetic energy and move more slowly; at higher temperatures, the molecules have higher kinetic energy and move more quickly.

Four temperature scales compared: Kelvin, Celsius, Rankine, and Fahrenheit.

Conductive heat flow H through a slab of material with conductivity k is given by Equation 4.1. Th and Tc are the temperatures on the warmer side and the cooler side of the slab, respectively. A is the slab area, and d is its thickness.

Class Review:Energy Update!EnergySociety

Next ClassForms of EnergyMaking EnergyQuantifying EnergyWorkFrictionEstimations

http://www.climate-leaders.org/climate-change-resources/climate-change/causes-of-climate-change

Factors that result from climate change and that can then amplify the causes of climate change are known as “positive feedbacks.” Some of the key positive feedbacks include thawing of permafrost (resulting in the release of previously trapped methane), forest loss due to drought (resulting in the release of carbon sequestrated in the wood) and the melting of the polar ice-caps (resulting in a reduced capacity to reflect solar energy from the earth’s surface)