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Thread: Defintions- Is this correct?

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    Defintions- Is this correct?

    Would this be the correct definition of ampere? I always assumed amps was quantity, or amount of electrons for a given period of time, or technically one columb per second.


    Ampere
    The ampere (symbol: A) is the unit used to measure
    current intensity.

    Second in this question would A and D be the correct answer? This is for a 3 volt circuit with a flash light bulb, knife switch and DD battery.


    Which of these could be used as a resistor in a circuit?

    a. a pencil
    b. a gas engine
    c. a rubber eraser
    d. an electric motor

    Third;

    Electrical insulators

    Some materials do not allow electricity to pass through
    them
    . These materials are known as electrical insulators.
    Plastic, wood, glass and rubber are good electrical
    insulators. That is why they are used to cover materials
    that carry electricity.
    Would changing the underline to "pass through them easily. " be more correct or is the definition still off?


    4th, would B and C work as an answer?
    10. Why is electrical wiring usually covered with a layer of plastic?

    a-To make it look pretty
    b-To help electricity flow along the wire
    c-To make it safe
    Just wondering if I could make these better. Working on a teaching tool.
    Last edited by mbrooke; 03-11-18 at 08:28 PM.
    I'm in over my head...

  2. #2
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    Quote Originally Posted by mbrooke View Post
    Would this be the correct definition of ampere? I always assumed amps was quantity, or amount of electrons for a given period of time, or technically one columb per second.
    ...
    ...
    Second in this question would A and D be the correct answer? This is for a 3 volt circuit with a flash light bulb, knife switch and DD battery.
    ...
    ...
    Third
    Would changing the underline to "pass through them easily. " be more correct or is the definition still off?
    ...

    Just wondering if I could make these better. Working on a teaching tool.
    1. Intensity is probably a poor word to use here, since it has a connotation of something per area or volume, something which has a value at a point.
    I would just say unit of current, period, and then make sure you have defined current as quantity of electric charge passing a demarcation (usually a surface) in one second. Historical note: for measurement purposes current was first actually defined in terms of the force between two parallel wire sections at a specific distance.

    2. I would say that you can use a motor as a resistor, if you ignore the inductance and do not let the motor spin (producing back EMF) or you can use the graphite core of the pencil as a high value resistor. There were some circuit kits at one time that had you draw your resistors on a substrate using a specific pencil. However in the context of a battery and light bulb I doubt that a typical pencil would allow the bulb to visibly light. You should perform that experiment.

    3. Definitely, since except at the quantum level there is no such thing as a perfect insulator.

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    Quote Originally Posted by GoldDigger View Post
    1. Intensity is probably a poor word to use here, since it has a connotation of something per area or volume, something which has a value at a point.
    I would just say unit of current, period, and then make sure you have defined current as quantity of electric charge passing a demarcation (usually a surface) in one second. Historical note: for measurement purposes current was first actually defined in terms of the force between two parallel wire sections at a specific distance.

    2. I would say that you can use a motor as a resistor, if you ignore the inductance and do not let the motor spin (producing back EMF) or you can use the graphite core of the pencil as a high value resistor. There were some circuit kits at one time that had you draw your resistors on a substrate using a specific pencil. However in the context of a battery and light bulb I doubt that a typical pencil would allow the bulb to visibly light. You should perform that experiment.

    3. Definitely, since except at the quantum level there is no such thing as a perfect insulator.

    This is why I love you guys! Spot on- I will include this explanation in the answer key after I tweak the wording.

    Technically for #2, even a spinning motor will act as a resistor in that it take energy to spin the mass of the armature across space and time?


    One more:

    10- Electrical energy can be stored in a ____________________. (also known as DC current)
    The correct answer is battery, however capacitor would work better here technically?

    My reasoning is that outside of a capacitor or static electricity across 2 mediums it is physically impossible to "store" electricity. A battery does not hold or store a charge, but rather chemicals that facilitate it.

    But then again, there is a potential across a charged battery, extra electrons on one plate a deficiency on another, so a battery is then storing electricity?
    I'm in over my head...

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    One thing I am thinking of explicitly explaining is that plastic/rubber is a poor conductor. Often good enough to do the job at 600 volts and under- but not something you want to use to handle high voltage in a lab experiment...
    I'm in over my head...

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    Quote Originally Posted by mbrooke View Post
    This is why I love you guys! Spot on.

    Technically for #2, even a spinning motor will act as a resistor in that it take energy to spin the mass of the armature across space and time?


    One more:



    The correct answer is battery, however capacitor would work better here technically?

    My reasoning is that outside of a capacitor or static electricity across 2 mediums it is physically impossible to "store" electricity. A battery does not hold or store a charge, but rather chemicals that facilitate it.

    But then again, there is a potential across a charged battery, extra electrons on one plate a deficiency on another, so a battery is then storing electricity?
    But a motor (if free to spin) will likely not provide a linear resistance.
    The fourth question is made totally unusable by the words in parentheses. Except in an inductor current has nothing to do with energy storage.
    You are correct that a battery stores chemical energy that can then be transformed into electrical energy. I would have to say capacitor or inductor as the two answers.

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    Quote Originally Posted by GoldDigger View Post
    But a motor (if free to spin) will likely not provide a linear resistance.
    My knowledge runs out here- can you clarify.

    The fourth question is made totally unusable by the words in parentheses. Except in an inductor current has nothing to do with energy storage.
    Got it- I was thinking DC would hint to a battery.


    You are correct that a battery stores chemical energy that can then be transformed into electrical energy. I would have to say capacitor or inductor as the two answers.
    You would be right.
    I'm in over my head...

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    Quote Originally Posted by mbrooke View Post
    My knowledge runs out here- can you clarify.
    Let's assume, for the moment, a DC motor. The relationship between applied voltage and current depends in a complex way on the way the stator and rotor are wound (shunt, series, or compound) and whether or not the motor is free to increase in speed or not (loading and control).
    If, OTOH, it is an AC induction motor connected to a constant power load, the current will actually decrease as the applied voltage is increased.

    Sent from my XT1585 using Tapatalk

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    Quote Originally Posted by GoldDigger View Post
    Let's assume, for the moment, a DC motor. The relationship between applied voltage and current depends in a complex way on the way the stator and rotor are wound (shunt, series, or compound) and whether or not the motor is free to increase in speed or not (loading and control).
    If, OTOH, it is an AC induction motor connected to a constant power load, the current will actually decrease as the applied voltage is increased.

    Sent from my XT1585 using Tapatalk
    I agree.
    I'm in over my head...

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    Quote Originally Posted by mbrooke View Post
    I agree.
    And that is not the behavior you expect from a resistor, which was the reason I argued it was not, on further examination, a valid resistor. It is a resistance, or more properly an impedance, but it is not a constant impedance which would allow useful calculations about what is going on in the circuit.

    For that matter, the light bulb is a very simple indication of applied voltage and current, but the resistance of the bulb varies with temperature.

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    Don't make the answers more complicated than they need be for the target audience.
    Si hoc legere scis nimium eruditionis habes.

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