Energy is measured in many ways. One of the basic measuring blocks is called a Btu. This stands for British thermal unit and was invented by, of course, the English. Btu is the amount of heat energy it takes to raise the temperature of one pound of water by one degree Fahrenheit, at sea level. One Btu equals about one blue-tip kitchen match. One thousand Btus roughly equals: One average candy bar or 4/5 of a peanut butter and jelly sandwich. It takes about 2,000 Btus to make a pot of coffee. Energy also can be measured in joules. Joules sounds exactly like the word jewels, as in diamonds and emeralds. A thousand joules is equal to a British thermal unit. 1,000 joules = 1 Btu So, it would take 2 million joules to make a pot of coffee. The term "joule" is named after an English scientist James Prescott Joule who lived from 1818 to 1889. He discovered that heat is a type of energy. One joule is the amount of energy needed to lift something weighing one pound to a height of nine inches. So, if you lifted a five-pound sack of sugar from the floor to the top of a counter (27 inches), you would use about 15 joules of energy. Around the world, scientists measure energy in joules rather than Btus. It's much like people around the world using the metric system of meters and kilograms, instead of the English system of feet and pounds. Like in the metric system, you can have kilojoules -- "kilo" means 1,000. 1,000 joules = 1 kilojoule = 1 Btu A piece of buttered toast contains about 315 kilojoules (315,000 joules) of energy. With that energy you could: • Jog for 6 minutes • Bicycle for 10 minutes • Walk briskly for 15 minutes • Sleep for 1-1/2 hours • Run a car for 7 seconds at 80 kilometers per hour (about 50 miles per hour) • Light a 60-watt light bulb for 1-1/2 hours • Or lift that sack of sugar from the floor to the counter 21,000 times! Energy can be transformed into another sort of energy. But it cannot be created AND it cannot be destroyed. Energy has always existed in one form or another.
another. Stored energy in a flashlight's batteries becomes light energy when the flashlight is turned on. Food is stored energy. It is stored as a chemical with potential energy. When your body uses that stored energy to do work, it becomes kinetic energy. If you overeat, the energy in food is not "burned" but is stored as potential energy in fat cells. When you talk on the phone, your voice is transformed into electrical energy, which passes over wires (or is transmitted through the air). The phone on the other end changes the electrical energy into sound energy through the speaker. A car uses stored chemical energy in gasoline to move. The engine changes the chemical energy into heat and kinetic energy to power the car. A toaster changes electrical energy into heat and light energy. (If you look into the toaster, you'll see the glowing wires.) A television changes electrical energy into light and sound energy. |
| How do we measure Energy? |
| Measuring Energy. |
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