This unit is designed for use with a sixth grade Science class over a period of three to four weeks. The primary objectives will be (1) understanding of a kilowatt-hour (2) learning how electric consumption is measured (electric meter) (3) learning how to read and record meter readings (4) to monitor daily electric consumption in the home (5) identify electric energy users and (6) understanding and calculating an electric bill.
It is suggested that this unit be part of a sequential development of Science concepts beginning with the theory of the atom in relation to the three states of matter. If we follow the basic curriculum for the city, we find that by beginning with the “basic building blocks” of nature, the atom, we can develop a curriculum which allows us to build and expand in many directions. The atomic theory is an excellent reference point, since everything around you is made up of extremely tiny atoms—the chair on which you sit, the pages of a book, etc. An atom is the smallest particle of matter that has distinct chemical and electrical characteristics. The atom is basically composed of three parts, the proton, neutron and electron. Electricity is a
of energy. We know what it is by what it does. It is important that the student understand that the atom is composed of electrically charged parts. The separation, frictional or chemical, of these parts creates an attraction or flow as a result of the particles re-uniting. This electron-proton flow thus creates a flow. Electrons are the smallest particles of electricity.
Electricity is not as awesome and difficult as we are led to believe. The atom is made up of a positive(proton) negative(electron) charge and a neutral neutron. Think word charge. What general impression does it bring to mind? The charge of an army? Moving with a force towards some goal. What makes electrons flow? How is this force created? This leads us to the two types of electricity: static and current. Static electricity to the sixth grader is a tangible, realistic concept that they can relate to with their experiences. For instance, lightning, shocks from wool carpets, balloons that stick to walls and static cling.
Everything is basically electrical and all matter consists of atoms which are composed of an electron, proton and neutron. It is important that the student realize that these particles are always equal, opposite and neutral. (The Law of Charges comes into effect.) This can be demonstrated by the fact that we don’t receive a shock from your desk, because the atoms are electrically neutral. Therefore the atomic structure is without charge or movement. They should be familiar with conductive materials which lose electrons easily. For instance, wool, silk, carbon, zinc and copper—materials which are used to make an electric cell. The problem now for the student is to understand how electrons and protons separate creating an electromotive force. Students should be familiar with current electricity, batteries, motors, generators, electromagnets, turbines etc. By this point, the student should have established the fact that electricity is the movement of electrons, resulting from either frictional or chemical imbalances.
Now we need a path for a charge (electron flow). An army wouldn’t just run all over the place. Their energies need direction, a path, so does the electron flow which we will call the current. Since current, in general terms, means a flow whether we are talking about wind, water or electricity, the path is called a circuit. With electricity, the end result may be music, pictures or some kind of work being done for us.
Current electricity works for people. In order to conduct electricity, atoms must have electrons that are free to move from atom to atom. Metals make good conductors because only the electrons move in metal conductors.
Now we have established that the charge is the moving factor in electricity. The path wire (circuit) is needed for direction. As something is needed to force these parts to move, we will call this the electromotive force. We are reminded that a force is a push or pull. The children know this fact if nothing else. Ask them, how many have been forced to do something that needed a little push or pull from someone? Now I have my force, my path (wire) and my destination—maybe a light, or TV.
Electric current in a circuit works much like a long hose with water. By connecting the hose to a faucet, spurts of water come out the far end almost immediately. You will have sent a signal from one end to the other. Now the flow (current) depends on three factors:
1. The pressure that causes the current flow or which we can measure in
2. The rate or amount of flow which we can measure in
3. The resistance of the conductor (wire) measured in
The flow produces a power measured in
. That is, they can do work.
In general, electrons travel through any conductor from a negative source to a positive source.
To summarize for the student in recognizable terms, we might say to the students: Listen. When your parents ask you to do some work it’s going to take some amount of energy. The energy you put into your work depends on how much
(electromotive force, or volt) is placed on you by your parents. The more force (volts) you use the more power you can exert. A powerful army is judged by the number of soldiers or volts that are in one place. If I direct this mighty force along a definite path (conductor) that has a beginning and end (circuit), the more powerful my power will be, What does it mean to be powerful? Everyone wants power. Obviously, the energy (volts) I put into a task, the more powerful I feel, the more work I do. If my charges or forces are scattered the less effective my output will be.
By no means has this been a complete background of electrical theory. This is not the intention of this unit. But I feel there must be a basic understanding of electrical concepts and theory to fully understand the intent of the major objectives of my unit.
At this point, we are primarily interested with measuring the input of electricity into our homes, which is recorded by the electric meter. In order to understand how this apparatus works, it is necessary to review the following units used to measure electricity. Each unit has a specific significance and the first three bear a relationship to each other:
is the unit that measures the potential difference in electrical force or “pressure” between two points on a circuit. The current, at most receptacles and lights, is at a moves from the hot supply wire through the load presented by an appliance or light, it loses voltage in doing work. When the current leaves the load and enters the return circuit provided by and is pressure, the dame as the earth.
is the unit used to measure the amount of current, that is, the number of electrically charged particles, called electrons, that flows past a given point on a circuit each second. If you could see the particles moving along a wire and could count to 6.28 billion in one second, then you would have counted enough particles to make 1 ampere. has an it completes the circuit and returns to the power plant.
is the unit of power. It indicates the rate at which a device converts electric current to another form of energy, either heat or motion, or to put it another way, the rate at which the device consumes energy.
is the unit of energy, measuring the total amount of electricity that is consumed. The relationship of volts, amperes and watts to one another is expressed in a simple equation that enables you to make any calculations you may need: Volts x amperes = watts. If the current is at 120V and a device requires 4 amps of current the equation will read: 120V x 4 amps = 480 watts.
To figure the current needed for a device rated in watts, turn the equation around: Watts x volts = amps. For example, if you have an appliance such as a toaster that uses 1200 watts: 1200 watts Ö 120 = 10 amps.
In order to help the students understand how the electricity reaches their homes, a diagram will be included demonstrating the path from the power plant to the home. (See diagram #1) At the service head, house wires connect to the utility wires and lead down the side of the house to a meter and then into the house to a service panel, from which power is distributed through the house by wiring systems called branch circuits. See diagram #2 for basic reference to demonstrate how the wiring is distributed throughout the home. Now the student has a basic conception of where the electricity comes from and how it is channeled around the house. At this point, I will begin discussion of the six major objectives of unit.