WEEK 1

We are going to explore electricity and electronics.

  • GOALS:
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    In order to do this we need to introduce some standard definitions. Since the subject matter is not simple, the student must read, listen to classmate's and instructor's comments, and experiment. The table below lists the concept that you need to try to understand. It is imperative that the student realizes that understanding is a multi faceted process. Especially be prepared to attack these ideas with experiments and questions.

    Name   Units Model
    Charge Q Coulomb Quantity of Water: Electric and magnetic forces are due to the presents of electric charge. This is something that has an amount associated with it. Just like you can measure the amount of water in a bucket, you can measure the amount of charge in a capacitor. In the same way that you can measure the amount of water that flows from a faucet in a minute you can measure the amount of charge that passes through a wire in one second.
    Voltage V Volt Height: Water towers lift water up to create the pressure necessary to push water through pipes. If you elevate the water to twice the height you get twice the pressure. We can understand the need for a push or pressure. Hopefully we can agree that the key to generating the pressure is the height of water. In electric circuits voltages are required to push charge through a circuit.
    Current I Amp Flow of Water: Current is the flow of electric charge. It is measured like all flows in terms of a quantity per second. You need to understand what flow means. A parade is the flow of people. If you draw a line across a street and measure the number of people in the parade that step over the line every minute you are measuring a flow. The flow can change, become negative and stop. This same idea applies to water moving through pipes and electricity.
    Resistance R Ohm Bottle Neck: With water flowing in a system you can create a bottle neck or a narrowing of the pipe. If you want to push water through the narrow pipe at the same rate of flow you need to provide a greater push. Once we are comfortable considering this type of bottleneck we can view all pipes or pathways as possessing the feature that a push is required to move water through. Large diameter pipes require a small push (small resistance). Small diameter pipes require a big push (large resistance).

     

    Introducing the concepts is just the beginning we must begin to connect our intuition based on our model with the properties of electric circuits. You should be asking question like: "If voltage is like height what would happen if I double the voltage". For that matter "Where does one get voltage ?".

    Voltage is provided by batteries and power supplies. Because most people have used batteries this is a good place to start. We will measure voltages with a multimeter. This will be an important instrument so we need to quickly become familiar with its use. One of your goals for the first lab will be to become comfortable measuring voltages using your multimeter.

    Another goal of the lab is to develop good recording or note taking skills. Most scientists keep logbooks or diaries that contain notes on how to perform measurements, ideas, results and warnings. Logbooks are personal and should be written in a style that matches your needs. You will all be given instructions on how to measure voltages with a multimeter. By the end of class you will have successfully taken some measurements. Based on the notes you record you should be able to pull a voltmeter off the shelf and measure the voltage of a battery without assistance next week. Your goal is to document the procedure so you can succeed in this endeavor. What I have seen from past years is that students do not record even the most basic information well. My first suggestion is draw a diagram or picture. Even if I have a manual with a photograph of a device I will often draw a picture of the device in my logbook. This forces me to notice how many knobs, how many plugs, and what types of settings are possible. Don't do an artist's rendering do a functional diagram. How can you represent the main features of the multimeter in a picture ? Note all the settings that you can find. Note the location of the cables, the color of the cables, and the way the value is displayed. In short make observations and record them. Take your time. Leave some space so you can update or clarify your diagram as you improve your knowledge in latter weeks.

    Some other topics you might want to refer to are:

     

    QUIZ *******

    In order to receive a grade of A you must successfully complete the lab portion of the course, read prelab material, and pass the lab quiz. In order to pass you must get 75% of the questions correct.

    In order to receive a grade of B you must successfully complete the lab portion of the course. The quiz is optional. For fun feel free to try the quiz.

    You are not allowed to consult with other students while taking the quiz. The quiz will be available at least from lab until following lab. You will be given 30 minutes to complete the quiz and you may refer to any written material.

    LON CAPA