DC Electric Circuits

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  • Question 1

    Identify some of the different types of capacitors, and their characteristics.

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  • Question 2

    How are electrolytic capacitors constructed, and what is particularly noteworthy about their use?

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  • Question 3

    A capacitor has a label on it saying, “100 WVDC”. What does this label mean? What is the consequence of exceeding this rating?

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  • Question 4

    Capacitors may pose an electric shock hazard, even in unpowered circuits. Explain why.

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  • Question 5

    Very large capacitors (typically in excess of 1 Farad!) are often used in the DC power wiring of high-power audio amplifier systems installed in automobiles. The capacitors are connected in parallel with the amplifier’s DC power terminals, as close to the amplifier as possible, like this:

    What is the purpose of having a capacitor connected in parallel with the amplifier’s power terminals? What benefit does this give to the audio system, overall?

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  • Question 6

    A 10 μF capacitor is charged to a voltage of 20 volts. How many coulombs of electric charge are stored in this capacitor?

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  • Question 7

    A 470 μF capacitor is subjected to an applied voltage that changes at a rate of 200 volts per second. How much current will there be “through” this capacitor?

    Explain why I placed quotation marks around the word “through” in the previous sentence. Why can’t this word be used in its fullest sense when describing electric current in a capacitor circuit?

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  • Question 8

    Two 470 μF capacitors connected in series are subjected to a total applied voltage that changes at a rate of 200 volts per second. How much current will there be “through” these capacitors? Hint: the total voltage is divided evenly between the two capacitors.

    Now suppose that two 470 μF capacitors connected in parallel are subjected to the same total applied voltage (changing at a rate of 200 volts per second). How much total current will there be “through” these capacitors?

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  • Question 9

    Suppose two 33 μF capacitors are connected in series with each other. What will their combined capacitance be, in Farads? Explain your answer.

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  • Question 10

    Calculate the total capacitance in this collection of capacitors, as measured between the two wires:

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  • Question 11

    Identify the following capacitor values and styles:

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  • Question 12

    When checked with an ohmmeter, how should a properly functioning capacitor respond?

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  • Question 13

    Find one or two real capacitors and bring them with you to class for discussion. Identify as much information as you can about your capacitors prior to discussion:

    Capacitance (ideal)
    Capacitance (actual)
    Voltage rating
    Type (mica, mylar, electrolytic, etc.)
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  • Question 14

    An important parameter in capacitor performance is ESR. Define ESR, and explain what causes it.

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  • Question 15

    Capacitors often have letter codes following the three-digit number codes. For example, here are some typical capacitor codes, complete with letters:


    Determine the meaning of letters used on capacitor labels, what the respective numeric values are for all the available letters, and then finally what these four specific number/letter codes mean (shown above).

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