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Have you ever wondered why shoes hanging on a power line don’t get fried? Or whether cars could someday run on cow manure? Now you can get answers to these and to all your energy- and water-related questions. Just Ask an Expert!

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NEW! Is it true that without a complete circuit you create heat?

Answer: An incomplete circuit does not create heat; in fact, it does not create anything! This is because a circuit that is not complete does not allow electricity to flow through it. Perhaps you are thinking of a “short circuit?” A short circuit can occur when wires lose their insulation and touch each other, allowing electricity to flow in a shorter path than intended. A short circuit can create enough heat to melt wires, and can even cause a fire.

How far can electricity flow?
—Mrs. Greene’s class

Answer: The main limit on how far electric current can flow in a circuit is the electrical resistance of the material it’s passing through. Resistance causes some of the energy in the current to be lost in the form of heat. Materials that are good conductors (like the copper wire used for power lines) offer low resistance. Materials like rubber are bad conductors—their resistance is so high that the current can’t flow much, if at all. But even copper has some resistance, and over longer distances more and more of the current’s energy will turn into heat.

The way power companies deal with this is to use very high voltage in their power lines. You can think of voltage in a power line as like the pressure in a water pipe—the higher the pressure, the further the water will flow. Some high-voltage power lines can carry electricity for as much as 2,000 miles!

That super-high voltage has to be lowered before it can power anything in your home or school. That’s done with transformers, which reduce the voltage to levels that can be used by lights and appliances.

What will happen if you touch electricity with wet hands?

Answer: Electricity travels easily through water. So touching anything electrical with wet hands makes it easier for electricity to travel through you, and increases your risk of suffering a painful or fatal shock! This is why you should always unplug toasters and other electrical appliances before you clean them, and why you should keep anything with a power cord away from bathtubs, puddles, sinks, and wet hands.

What role do electromagnets play in generating electricity?

Answer: To generate electricity, power plants use various energy sources, such as coal, natural gas, wind, or solar, to power turbines. The turbines turn electromagnets that are surrounded by heavy coils of copper wire. (Electromagnets are used because they're more powerful than magnetic iron, which the magnets you've probably played with are made of.) The moving electromagnets cause the electrons in the copper wire to move from atom to atom, generating electricity.

How do you measure electricity?

Answer: Electricity is measured in terms of amperage, voltage, and wattage. Amperage (amps for short) is a measure of the FLOW RATE of electricity used. Voltage (volts) measures the pressure, or FORCE, of electricity. The amps multiplied by the volts gives you the wattage (watts), a measure of the AMOUNT of electricity being used. Think of it this way: Electricity flowing through a wire is like water flowing through a garden hose. The amount of water that can fit through the hose depends on the diameter of the hose (amps). The pressure of the water depends on how far open the faucet is (volts). The amount of electricity being used (watts) depends on both the flow rate and the pressure of the water (volts x amps = watts).

What is chlorine? Why it is added in drinking water?

Answer: Chlorine is a common chemical element that can be found in a liquid, gas, or solid state. Chlorine gas can be mixed with water in precisely controlled amounts to kill disease-causing bacteria and microbiological organisms, which is why it is used around the world to disinfect drinking water supplies.

Why are there insulators on plugs?

Answer: There are insulators not only on plugs, but also on wires and everything of human design that conducts electricity. This is done in order to keep people from directly contacting the electricity that runs inside power cords and devices. Contact with electricity can shock, hurt, or even kill you! You can read more about how to be safe around toy, tool, and appliance wires and plugs in our website’s section, How Electricity Can Hurt You:

I once saw a pair of shoes hanging from a power line. Why didn’t the shoes get burned up by the electricity in the line?

Answer: Shoes hanging on a power line don’t get burned for the same reason that birds standing on a power line don’t get shocked: they don’t give electricity a path to the ground, so electricity stays in the line and does not go through them. But if the shoes were to touch a power line and a power pole at the same time, they would provide a path to the ground and would get blasted with electric current. It wouldn’t be pretty!

By the way, if you ever see someone throwing shoes up onto a line, tell them to stop! The shoes can damage the power line, or someone trying to get the shoes down could be seriously shocked or even killed.

Is it true that cars could someday run on cow manure?

Answer: Yes! Manure can be made into a gas containing methane. (Methane is the same energy-rich gas found in natural gas.) Certain types of bacteria emit this gas as they consume manure collected in special air-free tanks. The mixture of gases produced in this way, called biogas, can then be used in some modified car engines instead of gasoline, or burned in a boiler to generate heat or electricity.

Since the earth is covered with water, isn't there plenty of water for everyone?

Answer: Of all the water on earth, only about 3% is fresh water and only 1% is available for human consumption.

I have heard that landfills can be a source of energy. How does that work?

Answer: Organic waste emits methane as it decomposes—or rots—in the landfill. Landfills can collect and treat the methane and then sell it as a commercial fuel, or they can burn it to generate steam and electricity. Today, there are almost more than 600 gas energy landfill projects operating in the United States.

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