physics 161 - pages.uoregon.edu

Physics 161:

Physics of Energy and the Environment

Prof. Raghuveer Parthasarathy

[email protected]

Spring 2010

Physics 161:Physics of Energy & Environment R. Parthasarathy Spring 2010

Parthasarathy

Lecture 1: Announcements

• Homework: Problem Set 1 (on web page). Due Thurs. April. 1, 5pm.

• Office hours:– Prof Parthasarathy Tu 1.30‐2.30, Th. 10‐11, Will. 174; Extra office hours this week (RP) W. 1.30‐2.30 pm.

– GTF Matt Briel: W. 12‐1, Th. 1‐2pm, Willamette 216.

– GTF Mark Kuzyk: Tu 1‐2pm, W. 2‐3pm, Willamette 216.

• Lecture slides will be posted.


Lecture 1: Announcements

• Handout: Syllabus (later today)

• Email List Test: Did you receive the email I sent to the class list Monday afternoon? If not, check your uoregon.edu account; email me if you use some other address.

• Reading: “Guesstimation” excerpt; Wolfson, Chapter 2


Questions about Energy

• What is it?

• How do we use it?

• Why do we use it?

• What are the environmental consequences of our energy usage?

• What should we think about when we think about energy?


Energy Consumption (History)

• We use a lotmore energy than our own bodies produce.

• It wasn’t always like this:– ≈2 million years ago, metabolism / muscles (like other animals)

– ≈1.5 million years ago: fire – using energy stored in wood

– Work from domesticated animals (Oxen, 4000 B.C. ...)

– Since then, we’ve harnessed many types of fuels [Ask]


Fuels (& other energy sources)

• animal fats, oils

• flowing wind, water

• coal

• oil (petroleum)

• natural gas

• uranium

• solar energy

• etc.


Energy Consumption (History)

• We use a lotmore energy than our own bodies produce.

• How much more?


Energy – an exercise

• Let’s get a sense of scale for energy use

• Deep knee bends, or jump (high) – do it!

• Your body is working at a rate of ≈ 100 Watts (W), i.e. 0.1 kilowatts (kW)

(1 kW = 1000 W)


Human output: 100 W

• We’ll derive / calculate this later.

• An “order of magnitude” value – actual rate greater than 10’s of W, less than 100’s of W.

• Order of magnitude estimates are great!– Needless exactness is not a virtue, and can distract one from important broader issues

– We’ll practice using estimation


∗

What’s a Watt?

• A Watt is a unit of power

• Power is the rate of energy use

• Power and Energy are not the same thing!

• What is energy? We’ll define it later. For now: energy is the “stuff” that makes things happen – changes of speed, structure, etc.

• Power:Energy :: [X]:distance [Ask]

• Power:Energy :: speed:distance


What’s a Watt?

• Nonsense: “This appliance uses 500W of energy.” (Like: “This car traveled a distance of 70 mph.”)

• Nonsense: “This appliance runs at 500 Watts per hour.” (Like: “This car runs at 70 miles per hour per hour.”)


Power and energy

• Power is the rate at which energy is produced or consumed

• Power = Energy / Time

• (Rearranging:) Energy = Power × Time


∗

A unit of energy

• Power is the rate at which energy is produced or consumed Power = Energy / Time

Energy = Power × Time

• A common unit of energy: kilowatt‐hour (kWh)

• 1 kWh = 1000W × 1 hour• How long would you have to do knee‐bends to consume 1 kWh of energy (roughly)? [Ask]

• 1 kWh / 0.1 kW = 10 hours


Power and Energy

• We’ll say more about the meaning of power and energy, and other units for measuring them, later.

• Also, we’ll explain what we mean by “using”energy. (Energy isn’t really “used,” but converted from one form to another; some forms are more useful than others.)


Your energy consumption

• You, in a 21st century industrialized nation

• The key question: At what rate do you use energy?

• Think: light bulbs... heat / air conditioning... every truck carrying goods to stores for you... agriculture (tractors, etc.)... factories producing products...

• [...]


[Clicker Test]


Personal response systems (“Clickers”)

• “Real time” feedback / assessment

• Hip and Trendy

• Required! (1 clicker ⇔ 1 student). Participation grade (5%), starting next week. Also: used for quizzes.

Let’s try...

[Clicker Test]


What year are you?

A. Freshman (1st year)

B. Sophomore (2nd)

C. Junior (3rd)

D. Senior (4rd)

E. Other

Turn clicker on. Note lights.

[Clicker Test]


Have any of your other classes used clickers (this or previous terms)?

A. Yes

B. No

Turn clicker on. Note lights.

At what rate do you use energy?

What’s your guess?...

A. 100 W (102 W)

B. 1 kW (=1000 W = 103 W)

C. 10 kW (= 10,000 W = 104 W)

D. 100 kW (= 100,000 W = 105 W)


Handout on the web page: a refresher on scientific notation

The key question:


• The key question: At what rate do you use energy?

• About 10 kW (10,000 W).

• (A round number; more exact 11‐12 kW)

• This is the average rate at which you’re using energy, “around the clock, day in and day out.”



• 10 kW: about 100× the power one person can produce – i.e. you have ≈100 “energy servants”


• Of course, this power doesn’t come from people doing knee bends, but from coal plants, windmills, gasoline engines, ...

Your energy consumption – historyPhysics 161:Physics of Energy & Environment R. Parthasarathy Spring 2010

world average

Course outline• Energy usage

• Energy: What is it?

• Energy, Heat, and Thermodynamics

• Fossil Fuels and their Environmental Impacts

• Renewable energy sources (a brief look*)

• Nuclear Energy

• The Science of Climate

• Climate Change


* covered in depth in Phys. 162

Broader Goals

• Understanding Energy & the Environment

• Developing critical and quantitative reasoning skills.

• Not merely memorizing facts!


Syllabus

(Handout)


Clickers

Another comment on the clicker participationgrade:

Why is it there?

Small class: I can assess people’s learning individually.

Large class: statistics. What works for most of ≈130 people?

An interesting statistic...


ClickersLast term (Phys. 162), 24 out of 105 people had clicker scores < 50%. The clicker score counted for 7% of the overall class grade, so any of these people could have scored 93% in the class – a solid “A.”

How many scored over 70% (B‐ or higher)?


A. 20B. 10C. 5D. 1E. 0

A very strong correlation!


• At what rate do you use energy?

• About 10 kW (10,000 W).

• An important number.


Energy: Where are we?• What is the present energy situation? From what sources does the energy we use come from?

• (Note that I haven’t defined “energy” yet.)

• What fraction of the energy used in the U.S. comes from burning fossil fuels? (Guess):


A. 85%

B. 65%

C . 45%

D. 25%

natural gas, petroleum, coal

Your energy consumption – sources

• U.S. Average Mostly (85%) from fossil fuels.

• Oregon: more from hydroelectric power (half of electricity)

• “Other” (0.5%): geothermal, wind, solar

2004


In 2008: 1.0% (biggest increase: wind)

Where are we?

• What fraction of the energy used worldwidecomes from burning fossil fuels? (Guess):


A. 87%

B. 67%

C . 47%

D. 27%

≈ the same chart...

“≈” symbol: roughly equal

Your energy consumption – uses• What is this 10 kW used for?


Why use so much energy?

Increased standard of living

• Manufacturing goods

• Transport: trade, education, etc.

• Living comfortably


Why do you use so much energy?

• Also: Increases “quality of life.” ipods... travel... chocolate... (Hard to quantify.)

• Correlation between GDP, energy usage [graph next slide]; other measures also (e.g. “Human Development Index” (HDI)


GDP and Energy consumption

Physics 161

Power con

sumption (kWh/d/pe

rson

)

GDP per capita ($)

Graph from “Sustainable energy: without the hot air,”David McKay (2009)

Data from UNDP Human Development Report, 2007

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