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David conducts a study of electrical circuits. Segment length: 9:01 When it comes to understanding electricity, to get to the heart of the matter you must literally get to the heart of matter--the atom. Atoms are the building blocks of matter and they are composed of three particle types. The central core of the atom is called the nucleus and it contains positively charged particles called protons and neutral particles called neutrons. The movement of many charged particles in the same direction is called an electric current. Charged particles flow most easily through conductors, such as metals, or through some liquids, such as salt water. Electrons in metals are loosely attached to the atoms, so they can move easily. The human body (which is mostly salt water) is also a good conductor, which is why electric shocks can be so dangerous. Insulators, on the other hand, do not conduct electricity well. Their electrons are tightly bound to their atoms and do not move easily. Typical insulators include rubber, wood, glass, and most plastics. Electricity will only flow when a power source, such as a battery or a generator, sets the electrons in motion and when the electrons can complete a full circle. Consider this example--electrons flow from a battery down a wire to a light bulb, through the filament of the bulb, and then back up another wire to the battery. This closed loop is called a circuit. No electrical device, whether it's a simple flashlight or a complex computer, will work unless the circuit that delivers the electric current is a complete loop. Electricity becomes dangerous to you when you become part of the electrical loop--when the electrons have enough energy and make adequate contact to pass through your body. You can touch both ends of a flashlight battery and feel nothing, but if you're wet and in contact with household electricity, water can make a very good path through your skin and your body, making you part of the electrical circuit! Electrical energy always seeks the shortest route around the circuit back to the source, which in the above example is the battery. If the wires both touch a conductor, such as a metal tabletop, the electrons will take that shorter route back to the battery, rather than travel to the light bulb. (Conveniently, scientists call this a "short circuit.") So why don't birds get electrocuted when they sit on power lines? The power lines that are suspended in pairs between power poles are analogous to the wires that run between the battery and the light bulb. As long as birds sit on only one, they offer no "shortcut" to complete the circuit. But if their wings accidentally touch both adjacent power lines, the electrons take a new path and complete the circuit through the unfortunate bird's body! Imagine a world without electrical power. How would you cook, clean, and entertain yourself? Even though electrical energy is useful, its production often causes environmental problems. Acid precipitation from burning coal and disposal of nuclear waste are just two of them. What are some alternative power sources and how can conservation help minimize the damage?