HOMEMADE ELECTRONIC TESTER

Abstract
What do lamps, computers, televisions, printers, and kitchen appliances all have in common? They all need electricity to work. In order for electricity to provide power to these devices, it has to flow into and out of them. In this electronics science fair project, you will make your own simple circuit tester and use it to study how electricity flows through a lamp. Objective
The objective of this science fair project is to build a simple circuit tester and use it to investigate how electricity flows through a household lamp.
Introduction
Electricity is like water in a river, it flows. For example, when you turn on a lamp, electricity flows in through the power cord, then it flows through the light bulb, and finally, it flows back out through the power cord. Electricity flows through conductors. Most metals are good conductors. Copper is an excellent conductor, so it is used in power cords. To keep the electricity from flowing where it is not supposed to go, conductors that carry electricity are surrounded by insulators. Plastic and rubber are good insulators, which is why they are used to coat power cords. If electricity is like water flowing down a river, the conductors are like the sides of the river—they keep it within certain areas.
Electricity has to flow into and out of an object to provide power, and the path of the electricity is called a circuit. A circuit is a circular journey. In an electrical circuit, the electricity makes a circular journey through the device it is powering. For example, when a lamp is turned on, a circuit is formed from the socket in the wall, through the lamp, and then back to the socket. If the path of the electricity is broken, then the flow of electricity is stopped and the power to the device is turned off. The role of switches is to break the flow of electricity. A common type of switch has two pieces of metal that touch to make a circuit, and separate to break the circuit. More complex switches are used in electronic devices, but the basic idea is the same, they interrupt the flow of electricity.
You can test whether two objects are connected in a circuit using a device called a circuit tester (also called a continuity tester). In this electronics science fair project, you will make your own circuit tester. To determine if there is a path for electricity through a lamp, you will unplug it and attach probes to the prongs of the plug. When it is plugged in, electricity flows into the lamp from one prong and out through the other prong. By attaching your circuit tester to the two prongs, you can determine if there is a closed circuit for the flow of electricity. You will also determine how the lamp switch and the type of light bulb affect the flow of electrical current.
Terms, Concepts, and Questions to Start Background Research

• Conductor
• Insulator
• Circuit
• Switch
• Circuit tester
• Continuity tester
• Closed circuit
• Current
• Circuit diagram
• Alternating current

Questions

• What word is used by scientists to describe the flow of electricity? Hint: Think of the word for "moving water."
• How many types of switches can you find in your house?
• What is the definition of an open circuit?
• What is voltage?
• How are current and voltage related?
• What are some examples of good conductors and good insulators?