Energy, Power, and Transportation Technologies
Domain 5: Energy, Power, and Transportation Technologies
This domain tests energy forms and conversions, power and efficiency, energy sources, and the systems that move people and goods. Expect calculations and system-level reasoning about losses and impacts.
Core concepts
- Energy is the capacity to do work; power is the rate of energy transfer (P = E/t). Units include joules and watts.
- Forms include kinetic, potential, chemical, thermal, electrical, radiant, and nuclear. Energy is conserved but converts to less useful forms.
- Efficiency = useful output energy divided by input energy times 100 percent. Losses appear as heat, sound, and friction.
- Sources are renewable or nonrenewable; each has trade-offs in cost, availability, land use, emissions, and waste.
- Power systems include source, conversion, transmission, control, and load.
- Transportation systems include vehicle, guideway, propulsion, control, and support. Modes include land, water, air, and space.
Worked example
A motor draws 500 J of electrical energy and delivers 350 J of mechanical work. Efficiency = 350 divided by 500 times 100 percent = 70 percent. The remaining 150 J is mostly heat and sound. If the motor runs for 10 seconds, average input power = 500 J divided by 10 s = 50 W; useful output power = 35 W. The reasoning earns credit because it keeps energy in joules and power in watts separate, uses the correct denominator, and accounts for losses rather than claiming they disappear.
Traps
- Confusing energy with power.
- Reversing the efficiency ratio.
- Treating renewable as automatically low-impact.
- Forgetting transmission and conversion losses.
- Mixing kW and kWh.