Energy Flow in Technological Systems
Ms. Terkper's Digital Classroom — Science & Technology Emphasis
Focusing Questions
"Which came first, science or technology, and is it possible for technological development to take place without help from pure science? How did efforts to improve the efficiency of heat engines result in the formulation of the first and second laws of thermodynamics? How can the analysis of moving objects help in the understanding of changes in kinetic energy, force and work? Why are efficiency and sustainability important considerations in designing energy conversion technologies?"
Program Outcomes
Key Concepts
Unit Overview
The first and second laws of thermodynamics were useful in developing modern, efficient energy conversion devices. Students learn that while energy is conserved, useful energy diminishes with each conversion. Energy can only be observed when it is being transferred, and mechanical energy can be quantified.
History of Thermodynamics & Engines
Technology Before Theory
Key Idea
In thermodynamics, technology came before the science. Engineers improved heat engines through trial and error over centuries before scientists formalized the laws that explained why they worked. The science was derived from observing the technology.
| Year | Person | Contribution |
|---|---|---|
| 1698 | Thomas Savery | First practical steam pump (mining) |
| 1712 | Thomas Newcomen | Atmospheric steam engine; very inefficient |
| 1769 | James Watt | Separate condenser — dramatically improved efficiency; defined "horsepower" |
| 1824 | Sadi Carnot | Theoretical maximum efficiency of any heat engine (Carnot cycle) |
| 1850s | Clausius / Kelvin | Formal statement of both laws of thermodynamics |
Aboriginal Perspectives
Pre-contact First Nations and Inuit peoples applied sophisticated understandings of thermal energy and transfer in tool making, design of structures (e.g., igloos for insulation), and heating technologies — practical thermodynamic engineering that predates European formalization of these laws.
How Energy Concepts Were Discovered
Early scientists thought heat was an invisible fluid called "caloric." Rumford's cannon-boring experiment showed heat was limitless as long as boring continued — impossible if heat were a finite fluid.
Joule used a paddle wheel turned by falling weights to heat water. By measuring the temperature rise, he calculated: 4.18 J of mechanical work = 1 cal of heat.
James Watt observed that Newcomen's engine wasted energy re-heating the cylinder on every stroke. Adding a separate condenser kept the cylinder hot and increased efficiency dramatically.
Forms of Energy & Conversions
Major Forms of Energy
Energy of motion. Any moving object has kinetic energy. Ek = ½mv²
Examples: moving car, wind, flowing water
Energy due to position above a reference point. Ep = mgh
Examples: water in a dam, ball held up high
Energy stored in chemical bonds — a form of potential energy.
Examples: gasoline, food (glucose, ATP), batteries
Energy from random motion of particles (heat). Always produced as a "waste" in conversions.
Examples: friction, combustion heat, body heat
Energy carried by moving charges (current).
Examples: power grid, batteries, lightning
Energy carried by electromagnetic waves (light).
Examples: sunlight, infrared radiation
Energy carried as pressure waves through matter.
Examples: speaker, thunder, vibration
Energy stored in the nucleus of atoms, released by fission or fusion.
Examples: nuclear power plants, the Sun
Coal
Combustion
Steam/Turbine
Generator
Light Bulb
| Device | Input Energy | Output Energy | Waste |
|---|---|---|---|
| Car Engine | Chemical | Kinetic | Thermal |
| Hydroelectric Dam | Gravitational Pot. | Electrical | Thermal |
| Solar Panel | Solar | Electrical | Thermal |
| Light Bulb (LED) | Electrical | Light | Thermal |
| Wind Turbine | Kinetic | Electrical | Thermal |
| Nuclear Plant | Nuclear | Electrical | Thermal |
Evidence of Energy Transfer
Energy can only be observed when it is being transferred. Evidence that energy transfer is occurring includes:
- Change in motion (acceleration or deceleration)
- Change in shape (deformation, compression)
- Change in temperature (heat gained or lost)
- Observable physical or chemical changes
One-Dimensional Motion
| Quantity | Scalar or Vector? | Definition | SI Unit |
|---|---|---|---|
| Distance | Scalar | Total path length travelled | m |
| Displacement | Vector | Change in position (direction matters) | m |
| Speed | Scalar | Distance per unit time | m/s |
| Velocity | Vector | Displacement per unit time | m/s |
| Acceleration | Vector | Change in velocity per unit time | m/s² |
| Mass | Scalar | Amount of matter in an object | kg |
| Force | Vector | A push or a pull | N (kg·m/s²) |
| Work | Scalar | Force × displacement | J (N·m) |
Key Motion Definitions
Velocity = change in position ÷ change in time. Direction is important.
Acceleration = change in velocity ÷ change in time. Can be positive (speeding up) or negative (slowing down).
No net force is needed (in the absence of resistive forces). No energy input is required to maintain constant speed — only to overcome friction.
Reading Motion Graphs
- d-t graph: Slope = velocity. Horizontal line = at rest.
- v-t graph: Slope = acceleration. Area under line = displacement.
- Constant acceleration appears as a straight line on a v-t graph.
- Constant velocity appears as a horizontal line on a v-t graph.
Energy Equations & Work
Kinetic Energy Calculator
Gravitational Potential Energy Calculator
Work Calculator
Free Fall — Energy Conservation
The SI unit of energy and work is the joule (J). It is derived from:
1 J = 1 N × 1 m
1 N = 1 kg·m/s²
∴ 1 J = 1 kg·m²/s²
This confirms that energy and work share the same fundamental units, consistent with the work-energy theorem: ΔE = W
Laws of Thermodynamics & Efficiency
First Law of Thermodynamics
Conservation of Energy:
Energy cannot be created or destroyed; it can only be converted from one form to another. The total energy of an isolated system remains constant.
Consequence: You cannot build a perpetual motion machine that creates energy from nothing.
Second Law of Thermodynamics
Energy Degradation:
In every energy conversion, some energy is converted to thermal energy (heat) that cannot be fully recovered as useful work. Disorder (entropy) always increases.
Consequence: Heat engines are never 100% efficient — some energy always "leaks" as waste heat.
Efficiency Formula
Worked Efficiency Example
A car engine burns fuel containing 400,000 J of chemical energy and produces 100,000 J of useful kinetic energy. What is its efficiency?
Efficiency = 0.25 × 100% = 25%
Waste heat = 400,000 − 100,000 = 300,000 J
Why Can't Engines Be 100% Efficient?
The Second Law requires that heat always flows from hot to cold. In a heat engine, some of the thermal energy must be rejected to the cold reservoir (exhaust). This is not a design flaw — it is a fundamental law of nature.
~25%
~90%
~10%
~90%
~35%
~95%
~20%
~60%
| Fuel | Energy Content | Typical Efficiency | Cost | Environmental Impact | Sustainability |
|---|---|---|---|---|---|
| Coal | ~24 MJ/kg | ~35% | Low | High CO2, SO2, particulates | Not sustainable |
| Natural Gas | ~55 MJ/kg | ~50% | Medium | Lower CO2 than coal; cleaner burn | Limited |
| Hydroelectric | Varies with flow | ~90% | Low (operating) | Low emissions; habitat change | Renewable |
| Wind | Varies with wind | ~45% | Medium (capital) | Very low; some wildlife impact | Renewable |
| Solar (PV) | ~1400 W/m² | ~20% | Medium–High | Low (manufacturing impact) | Renewable |
| Nuclear | ~3.9M MJ/kg U | ~33% | High (capital) | Low emissions; waste disposal | Long-term concerns |
Interactive Practice & Quizzes
Knowledge Check Quiz
Test your understanding of energy, motion and thermodynamics.
Energy Flow — Science 10
Energy Conversion Match
Match each device on the left with its primary energy conversion on the right.
Vocabulary Flashcards
Click the card to flip it. Use the arrows to navigate.