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Homework Help: Design a wind turbine experiment at the High School level

  1. Nov 5, 2015 #1
    1. The problem statement, all variables and given/known data

    Plan an investigation to evaluate wind power as an energy source with equipment:

    • model wind turbine

    • multimeter to measure the voltage generated

    • anemometer to measure wind speed

    • hair dryer to generate wind power, set on cold

    • metre rule to measure distance.

    (i) Explain the aim of your investigation.

    (ii) Explain what you will measure.

    (iii) Explain the number and range of readings that you will take.

    (iv) Explain the independent variable.

    (v) Explain the dependent variable.

    (vi) Explain the control variables.

    (vii) Explain how you will make your experiment a fair test.

    (viii) Draw out a results table that you would use in your investigation.

    (ix) Write an evaluation identifying aspects of your experiment where modifications are possible.

    2. Relevant equations

    Section of High School physics book that I am reading is titled "Energy resources and energy generation"

    3. The attempt at a solution

    (i) Aim of investigation is to find out how increasing or decreasing wind speed changes the power output of the wind turbine. Hence decide if a light wind (hair dryer at a low setting) in an average town would be a good alternative fuel OR if only high winds (on a hill on in the sea) would generate adequate power.

    (ii) The turbine is effectively a battery so I would find out the voltage output of the turbine by connecting the voltmeter in parallel with it + connect an ammeter in series to find the current supplied.

    With voltage and current know I will know the power generated by the turbine from the formula P=IV

    I would measure the distance of hairdryer from turbine. The shorter the distance the more wind (if i can't just control the wind with a button on the side of the dryer).

    (iii) Number and range of readings : Repeat 3 times (DON'T KNOW WHY - just sounds right).

    Maybe measure the distance of the hairdryer from the turbine.

    (iv) Independent variable is the voltage output (and current supplied ??).

    (v) Dependent variable is the distance of hair drier from the turbine (i.e strength of wind)

    (vi) Control variable is the distance of hair dryer from turbine.

    (vii) To make the experiment a fair test : repeat the experiment 3 times ??? Use the same same sized blades on the turbine for each change of wind speed.

    (viii) Table used in investigation would include list of voltages produced, current flowing, distance of hairdryer from propellers.

    (ix) Evaluation of modifications would be to include a light bulb in a series circuit from generator to buld and back to generator to see how the bulb lit up with different winds.

  2. jcsd
  3. Nov 5, 2015 #2


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    Staff: Mentor

    Sounds like a fun project! :smile:

    But how big is your "turbine" going to be? You won't get a very wide airflow out of a hair dryer. And efficiency depends pretty strongly on the size of the turbine. If you make your measurements with a 3 inch turbine, that won't tell you good numbers for a 3 foot turbine.

    Also, have you learned much yet about basic circuits and electricity? When you have a source of power like a battery or an electric generator, that source has a "source resistance" effectively in series with the source voltage. You get maximum power transfer when the external load is equal to the source resistance. So you can't just hook up any old resistor outside and measure the resulting load current and load voltage to find the power output of the generator. You'd want to match the load resistor to your generator's source resistance -- that will give you the maximum output power.

    You can do some reading about "maximum power point" for solar panels, for example, to learn more about that concept. It would be an important thing to include in your report and experiments.
  4. Nov 5, 2015 #3
    Its not a project. Its just questions about a hypothetical project in a book.

    Unfortunately, I don't know What you're saying to me. I understand the individual words (voltage, power etc) but combined in a sentence it all sounds like gobbledygook. Its me .... not you.:sorry::oops:

    Don't understand these bits : "source resistance" effectively in series with the source voltage.

    "You get maximum power transfer when the external load is equal to the source resistance".

    "So you can't just hook up any old resistor outside and measure the resulting load current and load voltage to find the power output of the generator".

    "You'd want to match the load resistor to your generator's source resistance -- that will give you the maximum output power"

    Quite embarrassing because I thought I had answered the question well
    Last edited: Nov 5, 2015
  5. Nov 5, 2015 #4


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    Science Advisor
    Homework Helper
    Gold Member

    There is a key item missing from your attempt (and it doesn't seem to have been requested). You need to design the experimental set-up. That includes an electrical circuit.
    You cannot measure the power output unless you have a current. Placing a voltmeter across the terminals will not permit a current. You need to add a sample load, i.e. a known resistance across the terminals. It needs to be a big enough resistance that you won't burn it out (P=V2/R).
    The generator will itself have an internal resistance. You can observe this in the fact that if you lower the load resistance the current will go up but the voltage will go down. The maximum output power (i.e. the power dissipated in the load) occurs when the load resistance equals the internal resistance. However, this does not mean you need to choose a load resistance matching the internal (source) resistance. Instead, you can just measure the power at a couple of different values of external (load) resistance and compute the power for any other load.
    You don't really care about that. What you care about is the windspeed at the turbine. It won't be obvious how this depends on distance, and besides you can measure it directly with the anemometer.
    You have that backwards. The independent variable(s) is/are the ones you as experimenter can directly vary. The dependent variables are the measured consequences.
    See https://en.wikipedia.org/wiki/Control_variable
    The issue of maximising power output would be relevant here. Do you see why?
  6. Nov 6, 2015 #5
    Thanks. I'll try again with advice given:

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