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AGC/United Learning • 1560 Sherman Ave., Suite 100 • Evanston, IL 60201 • 800-323-9084

CHEMICAL POTENTIAL ENERGY STORED IN COAL TO THERMAL ENERGY. THE THERMAL ENERGY IS TRANSFERRED TO WATER, WHICH IS CONVERTED TO STEAM. THE STEAM DRIVES A TUR- BINE, WHICH IN TURN DRIVES A GENERATOR. THE GENERA- TOR CONVERTS KINETIC ENERGY INTO ELECTRICITY. LAUREEN: THE PLANT USES 411 TONS OF COAL PER HOUR, WITH A THERMAL VALUE OF 18.5 GIGAJOULES PER TON. BRENDON: SO THAT’S AN INPUT VALUE OF 411 TONS PER HOUR, TIMES 18.5 GIGAJOULES PER TON, OR 7.604 TIMES 10 TO THE 12 JOULES PER HOUR. LAUREEN: AND THE OUTPUT OF THE PLANT IS 2.6 TIMES 10 TO THE 12 JOULES PER HOUR. SO THE EFFICIENCY IS: OUTPUT, 2.6 TIMES 10 TO THE 12 JOULES PER HOUR, DIVIDED BY INPUT, 7.604 TIMES 10 TO THE 12 JOULES PER HOUR, TIMES 100%. BRENDON: WHICH IS 0.342 TIMES 100%, OR 34%. SARAH: SO HOW DO THEY COMPARE? LAUREEN: NO CONTEST! SARAH: SO FINDING THE EFFICIENCY OF A SYSTEM IS REALLY MOST VALUABLE WHEN WE USE IT TO COMPARE ONE SYSTEM WITH ANOTHER. BRYCE: SO, CRAIG, WHAT ARE THE FACTORS AFFECTING EFFI- CIENCY ON THE SKI TRAIL? CRAIG BULAWKA: THE BIGGEST ONE IS BIOMECHANICS — HOW WELL YOU EXECUTE THE STRIDE...AND THE TYPE OF WAX YOU CHOOSE, THE TEMPERATURE OF THE SNOW — BRYCE: YEAH. CRAIG BULAWKA: FRICTION CAUSED BY CLOTHING, AND WIND RESISTANCE — SKIING AGAINST THE WIND REALLY WASTES A LOT OF ENERGY. BRYCE: YEAH. DARREN: A CAR CONVERTS THE CHEMICAL POTENTIAL EN- ERGY OF GASOLINE INTO THE KINETIC ENERGY OF TRAVEL. SO TO MAKE IT RUN MORE EFFICIENTLY, THE ENGINE SHOULD BE TUNED UP. THE AMOUNT OF AIR RESISTANCE A CAR EN- COUNTERS ON THE ROAD CAN HAVE A BIG INFLUENCE ON ITS EFFICIENCY. SO THE DESIGN OF THIS CAR IS MORE EFFICIENT THAN, SAY, A BUS! COLLEEN: A PLANT TAKES IN RADIANT ENERGY FROM THE

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