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confused about circuitry
Last Post 25 Feb 2012 09:05 PM by Yomero. 7 Replies.
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ihaveaquestion
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23 Feb 2012 07:19 PM
    I know that connecting the + and - terminals of a battery creates a short circuit, but this ultimately has to happen for current to flow. Does this mean that all dc circuits using batteries are short cicuits, because the + and - ends have to touch, or what has to happen to avoid a "short" dc circuit? Please explain as I am completely confused
    Yomero
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    23 Feb 2012 08:32 PM
    Content deleted by moderator. This is a professional forum, members need to act that way.

    Niel Leon
    Engineering.com (Forum Moderator)
    ihaveaquestion
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    24 Feb 2012 06:51 AM
    Content deleted by moderator since it is now not necessary.

    Thank you for your question, see the good response below.

    Niel Leon
    engineering.com
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    jwd217
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    24 Feb 2012 08:31 AM
    Electricity is part of engineering, i.e. Electrical Engineering. The term "short" refers to an electrical connection that is not wanted. This would be the case if you just connected the + and - terminals of a battery together. If you connect the + and - terminals to a light bulb the current flows through the bulb but is not called "short" because it is a wanted connection. The light bulb filament has much more resistance to the flow of current than a wire does so it lights the bulb but does not cause a problem. A normal incandecent 100watt light bulb has 144 ohms of resistance. So if connected to 120 volts, it would pull about .833 amp of current. A wire without a bulb would have close to zero ohms, a short, and would pull a huge amount of current and trip a 15 to 20 amp breaker. Example, a wire with 1 ohm would pull 120 amps. Most wires are much less than 1 ohm and would pull much more.

    P.S. I have seen a lot of silly questions on this forum, but this is not one of them.
    Niel
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    24 Feb 2012 12:48 PM
    jw:

    Thank you for your excellent response.

    Niel
    ihaveaquestion
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    24 Feb 2012 01:40 PM
    Thanks a lot! This was exactly what I was trying to understand. I apologize for my comment to the other user I didn't mean to start a problem on here
    Niel
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    25 Feb 2012 01:55 PM
    IHQ:

    You did not cause a problem the other person did.

    Thank you for understanding and being tolerant. Your comment was very good and shows maturity.

    Good luck with life and with your studies.

    Niel Leon
    engineering.com
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    Yomero
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    25 Feb 2012 09:05 PM
    According to the American Institute of Physics (AIP), one of the Physics textbooks most used in the US is Conceptual Physics, by Paul G. Hewitt.
    How do I know this book? Because my two teen age children have used it, and I regularly help them with their homework.
    This textbook, Part-V, Chapters 22 through 25, describe the physics of electricity and magnetism. Chapter 23 is titled "Electric Current" This chapter contains a very graphic explanation to your questions, with much detail about current, resistance, how batteries are used, etc.
    Perhaps I was rude in my first answer. That was unintended.
    The point I was trying to make is that much of the information is available in textbooks, and surprisingly to many (including me), it is provided to most students since the early days of high school.

    In my high school days, if my memory serves me right, we were playing with batteries and AC power so many times that we were actually doing dangerous things with electricity, precisely because we were experimenting (toying is a more accurate term) with short circuits. We learned very quickly what a short circuit was, and how careful we needed to be when working with electricity. But we did not have such beautiful textbooks as those used today. In those days, we received everything from our teachers, and luckily, they were very good.

    I have recently been exposed to young students in their first college year at the local university. One of the biggest surprises I have experienced is that many of them (I am older, working on a graduate program) appear to have forgotten everything they learned in high school, not just about Physics, but also about Math in general. They need a lot of help during their first year to bring them up to speed for the first courses they will be taking if they choose engineering, electrical engineering in particular.
    Finally, if the Forum Moderator allows, my initial comment was in no way intended to upset anyone, but a knee-jerk type reaction on my side to the question I saw here.
    Sometimes it is a little discouraging to see little activity in forums like this,(take a look at the forums in the IEEE website, which is global and yet there is little activity there) in a website that actually has some fresh content that catches the attention of the visitor.
    I got here because of the Videos section above. I have enjoyed so much the creativity they have in those videos. I hope to be able to participate in this forum to share enthusiasm towards electrical engineering. There is su much to learn, and time seems so short to study it........

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