electricity

As weve already discussed, a generator converts mechanical energy into electricity. A motor works on the same principles, but in the opposite direction it converts electrical energy into mechanical energy. To do this, a motor needs a special kind of magnet known as an electromagnet. In its simplest form, this consists of an iron bar wrapped in a coil of wire. If you pass an electric current through the wire, a magnetic field is formed in the iron bar, and it becomes a magnet, with definite north and south poles. Turn off the current, and the magnetic properties disappear. By themselves, electromagnets are useful things. You can use them to pick up metal objects, carry the objects somewhere and then drop them by just turning off the power. For example, roofers use them to pick up nails that have fallen by accident into a homeowners yard. And wrecking yards have cranes with built in electromagnets strong enough to pick up and move entire cars.

Electromagnets are especially useful when theyre placed on an axis between two stationary magnets. If the electromagnets south pole is situated against the south pole of one stationary magnet and its north pole against the north pole of the other stationary magnet, the electromagnet will rotate until opposite poles line up. This wouldnt be very helpful, except the polarity of electromagnets depends on the direction of current flow. Pass electric current in one direction, and the magnets north pole will be on one side; reverse the current flow, and the north pole will be on the opposite side. In motors, a device known as a commutator reverses the direction of flow of electric current. As the poles of the electromagnet flip back and forth, the magnet is able to rotate without interruption. This is a brief explanation of course, so you may want to read How Electric Motors Work for all of the details.

As it turns out, the mechanical energy created in an electric motor can be put to good use in a variety of machines. Many tools in your garage, appliances in your house and toys kids play with rely on motors. Some of these motors require a large current to operate. Others, such as small DC motors used in robots and models, need very little voltage or current to perform efficiently. Well continue our conversation about voltage and current in the next section.

As mentioned earlier, the number of electrons in motion in a circuit is called the current, and its measured in amps. The pressure pushing the electrons along is called the voltage and is measured in volts. If you live in the United States, the power outlets in the wall of your house or apartment deliver 120 volts each.

If you know the amps and volts involved, you can determine the amount of electricity consumed, which we typically measure in watt hours or kilowatt hours. Imagine that you plug a space heater into a wall outlet. You measure the amount of current flowing from the wall outlet to the heater, and it comes out to 10 amps. That means that it is a 1,200 watt heater. If you multiply the volts by the amps, you get the wattage. In this case, 120 volts multiplied by 10 amps equals 1,200 watts. This holds true for any electrical appliance. If you plug in a light and it draws half an amp, its a 60 watt light bulb.

Lets say that you turn on the space heater and then look at the power meter outside. The meters purpose is to measure the amount of electricity flowing into your house so that the power company can bill you for it. Lets assume we know its unlikely that nothing else in the house is on, so the meter is measuring only the electricity used by the space heater.

Your space heater is using 1.2 kilowatts 1,200 watts. If you leave the space heater on for one hour, you will use 1.2 kilowatt hours of power. If your power company charges you 10 cents per kilowatt hour, then the power company will charge you 12 cents for every hour that you leave your space heater on.

Now lets add one more factor to current and voltage resistance, which is measured in ohms. We can extend the water analogy to understand resistance, too. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate and the resistance is like the pipe size.

something called direct current DC. The positive and negative terminals of a battery are always, respectively, positive and negative. Current always flows in the same direction between those two terminals.

The power that comes from a power plant, on the other hand, is called alternating current AC. The direction of the current reverses, or alternates, 60 times per second in the U.S. or 50 times per second in Europe, for example. The power that is available at a wall socket in the United States is 120 volt, 60 cycle AC power.

The big advantage that alternating current provides for the power grid is the fact that it is relatively easy to change the voltage of the power, using a device called a transformer. Power companies save a great deal of money this way, using very high voltages to transmit power over long distances.

How does this work? Well, lets say that you have a power plant that can produce 1 million watts of power. One way to transmit that power would be to send 1 million amps at 1 volt. Another way to transmit it would be to send 1 amp at 1 million volts. Sending 1 amp requires only a thin wire, and not much of the power is lost to heat during transmission. Sending 1 million amps would require a huge wire.

So power companies convert alternating current to very high voltages for transmission such as 1 million volts, then drop it back down to lower voltages for distribution such as 1,000 volts, and finally down to 120 volts inside the house for safety. As you might imagine, its a lot harder to kill someone with 120 volts than with 1 million volts and most electrical deaths are prevented altogether today using GFCI outlets. To learn more, read How Power Grids Work.

When the subject of electricity comes up, you will often hear about electrical grounding, or just ground. For example, an electrical generator will say, Be sure to attach to an earth ground before using, or an appliance might warn, Do not use without an appropriate ground.

It turns out that the power company uses the Earth as one of the wires in the power system. The planet is a good conductor, and its huge, so it makes a handy return path for electrons. Ground in the power distribution grid is literally the ground thats all around you when you are walking outside. It is the dirt, rocks, groundwater and so on.

If you look at a utility pole, youll probably be able to spot a bare wire coming down the side of the pole. This connects the aerial ground wire directly to ground. Every utility pole on the planet has a bare wire like this. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole. That coil is in direct contact with the earth once the pole is installed, and is buried 6 to 10 feet 2 to 3 meters underground. If you examine a pole carefully, you will see that the ground wire running between poles are attached to this direct connection to ground.

Similarly, near the power meter in your house or apartment there is a 6 foot 2 meter long copper rod driven into the ground. The ground plugs and all the neutral plugs of every outlet in your house connect to this rod. Our article How Power Grids Work also talks about this.

Imagine a pure gold ring. Divide it in half and give one of the halves away. Keep dividing and dividing and dividing. Soon you will have a piece so small you will not be able to see it without a microscope. It may be very, very small, but it is still a piece of gold.

If you could keep dividing it into smaller and smaller pieces, you would finally get to the smallest piece of gold possible. It is called an atom. If you divided it into smaller pieces, it would no longer be gold. Everything around us is made of atoms and scientists so far know of 118 different kinds. These different kinds of atoms are called elements. There are 98 elements that exist naturally although some are only found in very small amounts. Four of these 118 elements have reportedly been discovered, but have not yet been confirmed. Atoms join together in many different combinations to form molecules, and create all of the materials you see around you.

Protons, neutrons and electrons are very different from each other. They have their own properties, or characteristics. One of these properties is called an electrical charge. Protons have what we call a positive + charge. Electrons have a negative charge. Neutrons have no charge, they are neutral.

The charge of one proton is equal in strength to the charge of one electron. When the number of protons in an atom equals the number of electrons, the atom itself has no overall charge, it is neutral.

There are two types of Electricity, Static Electricity and Current Electricity. Static Electricity is made by rubbing together two or more objects and making friction while Current electricity is the flow of electric charge across an electrical field.

Static Electricity

Static electricity is when electrical charges build up on the surface of a material. It is usually caused by rubbing materials together. The result of a build up of static electricity is that objects may be attracted to each other or may even cause a spark to jump from one to the other. For Example rub a baloon on a wool and hold it up to the wall. Before rubbing, like all materials, the balloons and the wool sweater have a neutral charge. This is because they each have an equal number of positively charged subatomic particles protons and negatively charged subatomic particles electrons. When you rub the balloon with the wool sweater, electrons are transferred from the wool to the rubber because of differences in the attraction of the two materials for electrons. The balloon becomes negatively charged because it gains electrons from the wool, and the wool becomes positively charged because it loses electrons.

Current Electricity

Current is the rate of flow of electrons. It is produced by moving electrons and it is measured in amperes. Unlike static electricity, current electricity must flow through a conductor, usually copper wire. Current with electricity is just like current when you think of a river. The river flows from one spot to another, and the speed it moves is the speed of the current. With electricity, current is a measure of the amount of energy transferred over a period of time. That energy is called a flow of electrons. One of the results of current is the heating of the conductor. When an electric stove heats up, its because of the flow of current. There are different sources of current electricity including the chemical reactions taking place in a battery. The most common source is the generator. A simple generator produces electricity when a coil of copper turns inside a magnetic field. In a power plant, electromagnets spinning inside many coils of copper wire generate vast quantities of current electricity. There are two main kinds of electric current. Direct DC and Alternating AC. Its easy to remember. Direct current is like the energy you get from a battery. Alternating current is like the plugs in the wall. The big difference between the two is that DC is a flow of energy while AC can turn on and off. AC reverses the direction of the electrons.

Some atoms have electrons that can flow easily from one atom to another, such as metal. This is why metal is used in wires that conduct electricity. Other materials, such as rubber, have atoms that resist the flow of electricity, and that

These parts of an atom have a positive charge. They are in the middle of the atom, called the nucleus and they do not move.

These parts of an atom have no charge. They are neutral and part of the nucleus of an atom with the protons.