_Kilowatts_--Your electric bill usually reads in kilowatt hours. A kilowatt is 1000 watts. A kilowatt hour equals 1000 watts used for 1 hour. One kilowatt equals about 1-1/3 horsepower. A kilowatt is usually indicated by "kw" and a kilowatt hour by "kwh." _Circuits_--A closed circuit is one in which the electricity is flowing, lighting a light, running a motor, or some other appliance. The circuit runs all the way from the place the electricity is being generated to your home, through the appliance or light bulb, and back to the generator. Circuits are opened and closed by switches. When the circuit is opened, the electricity stops at the switch. Before working on a switch, socket, fuse, or any part of the wiring be sure to open the main switch. The main switch is usually at the fuse box or near it. Appliances should be disconnected when you work on them. Everyone in the family should know where the main switch is so it can be pulled in case of accidents, fire, flood, or windstorm damage. _Fuses and Circuit Breakers_--These are the safety valves of your electrical system. The different electrical circuits in your home are meant to carry only certain amounts of electricity. Some carry only 15 amps, others can carry 20 or more. They are marked to show capacity. When a fuse burns out or a circuit breaker opens, look for an overload of lights and appliances on the circuit before you try to replace the fuse or close the circuit breaker. Without these safeguards, the overloaded electric line will heat up and may start a fire. Even if no fire starts, electricity will be wasted and the homeowner will be paying for electricity that's doing no good. Remember: If you ever have to replace a fuse, pull the main switch first. Keep a flashlight handy in your house. It seems that fuses usually blow at night, and it doesn't pay to stumble or fumble around electric wires in the dark. WHAT TO DO: Make A Circuit Board So that you can show others how electricity travels from here to there, and how it behaves under different conditions, make an electric circuit board. _Materials Needed:_ Piece of 3/4" board about 4" x 6" l-l/2-volt No. 6 dry cell battery Two pieces of bell wire, each 24" long, one black, one white Two 10-penny box nails (3") Three 3-penny box nails (1") Two small screws or carpet tacks Two 2-inch rubber bands Two miniature sockets with solder terminals Two l-l/2-volt flashlight bulbs _Tools Needed:_ Ruler, pencils, hammer, pliers or vise. _Making the Board:_ 1. Lay out the board with a pencil and ruler as indicated in Figure 1. 2. Bend the three-inch nail as shown in Figure 2, using pliers, vise and hammer.