Transformation of Energy
Transformation of Energy
The transformation of energy from one form into others is happening all the time. The chemical energy in food is converted into thermal energy through metabolism; light energy is converted into chemical energy through photosynthesis. In a larger example, the chemical energy contained in coal is converted into thermal energy as it burns to turn water into steam in a boiler. This thermal energy in the steam in turn is converted to mechanical energy as it spins a turbine, which is connected to a generator to produce electrical energy. (In all of these examples, not all of the initial energy is converted into the forms mentioned. This important point is discussed later in this section.)
Another example of energy conversion occurs in a solar cell. Sunlight impinging on a solar cell (see the figure below) produces electricity, which in turn can be used to run an electric motor. Energy is converted from the primary source of solar energy into electrical energy and then into mechanical energy.
Solar energy is converted into electrical energy by solar cells, which is used to run a motor in this solar-power aircraft. (credit: NASA)
Energy of Various Objects and Phenomena
| Object/phenomenon | Energy in joules |
|---|---|
| Big Bang |
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| Energy released in a supernova |
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| Fusion of all the hydrogen in Earth’s oceans |
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| Annual world energy use | \(4×{\text{10}}^{\text{20}}\) |
| Large fusion bomb (9 megaton) | \(3\text{.}8×{\text{10}}^{\text{16}}\) |
| 1 kg hydrogen (fusion to helium) | \(6\text{.}4×{\text{10}}^{\text{14}}\) |
| 1 kg uranium (nuclear fission) | \(8\text{.}0×{\text{10}}^{\text{13}}\) |
| Hiroshima-size fission bomb (10 kiloton) | \(4\text{.}2×{\text{10}}^{\text{13}}\) |
| 90,000-ton aircraft carrier at 30 knots | \(1\text{.}1×{\text{10}}^{\text{10}}\) |
| 1 barrel crude oil | \(5\text{.}9×{\text{10}}^{9}\) |
| 1 ton TNT | \(4\text{.}2×{\text{10}}^{9}\) |
| 1 gallon of gasoline | \(1\text{.}2×{\text{10}}^{8}\) |
| Daily home electricity use (developed countries) | \(7×{\text{10}}^{7}\) |
| Daily adult food intake (recommended) | \(1\text{.}2×{\text{10}}^{7}\) |
| 1000-kg car at 90 km/h | \(3\text{.}1×{\text{10}}^{5}\) |
| 1 g fat (9.3 kcal) | \(3\text{.}9×{\text{10}}^{4}\) |
| ATP hydrolysis reaction | \(3\text{.}2×{\text{10}}^{4}\) |
| 1 g carbohydrate (4.1 kcal) | \(1\text{.}7×{\text{10}}^{4}\) |
| 1 g protein (4.1 kcal) | \(1\text{.}7×{\text{10}}^{4}\) |
| Tennis ball at 100 km/h | \(\text{22}\) |
| Mosquito \(\left({10}^{–2}\phantom{\rule{0.25em}{0ex}}g at 0.5 m/s\right)\) | \(1\text{.}3×{\text{10}}^{-6}\) |
| Single electron in a TV tube beam | \(4\text{.}0×{\text{10}}^{-\text{15}}\) |
| Energy to break one DNA strand | \({\text{10}}^{-\text{19}}\) |
This lesson is part of:
Work, Energy and Energy Resources