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Homework Help: Some Easy Questions About Electricity

  1. Dec 18, 2011 #1
    These are some questions which my teacher told us would likely be on a test tomorrow.

    I'd just like to know the best possible answers for them, as I have a general idea but I'd like to be sure.

    1. Why are loads connected in a household in parallel rather than series?

    2. Why must transformers use AC to work?

    3. How do transformers use safe and efficient distribution methods for electrical energy?

    4. Describe the basis of electrical generation.

    5. Describe the historical reasoning from electrical current and why it goes in the opposite direction?

    Thanks a lot guys!
  2. jcsd
  3. Dec 18, 2011 #2

    Simon Bridge

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    Welcome to PF.
    That's not really what we do here - if we did, we'd basically be taking your test for you.
    At the very least it turns this part of your test into an exercize in memorizing the "best possible answers".

    What you can do is post your ideas and we can help you over any misconceptions you have.
  4. Dec 18, 2011 #3
    Fair enough.

    Here are my answers:

    1. This allows different loads to be turned on individually, also allowing the voltage to remain constant throughout the house.

    2. A transformer will only work with AC because in order for it to work it requires a constant magnetic field.

    3. More current means bigger and more expensive wire, causing the use of less current and more voltage to be more energy and cost efficient. Transformers are used to step voltage up then down, by stepping them down it increases the safety and lowers the chance of electrocution.

    4. Whenever an electric current moves through a conductor, a magnetic field is created in the region around the conductor. Electromagnetic conduction means a current is conducted whenever the field in which the conductor is in change, for example spinning a magnet around a coil or a coil around a magnet, though they must be perpendicular to each other.

    5. A scientist deduced that two charges repelled or attracted each other. He claimed too much charge was positive and too little charge was negative. Later we realized too much charge is negative (too many electrons), and too little charge is positive (not enough electrons).

    Unfortunately, as I was away on holidays for most of this unit, all of these answers have been self taught from the textbook or just from my previous (and basic) knowledge of electricity.

    Are there any glaring errors or misconceptions you can see there?
  5. Dec 18, 2011 #4


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    on 1, what happens if an "on" device blows out?

    on 2, I think you should look into this a bit more
  6. Dec 18, 2011 #5


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    Staff: Mentor

    Yes, also it allows all the loads to be designed for a particular, fixed voltage.
    Make that transformers require a VARYING field to operate. The changing field of the primary causes a changing field for the secondary, which in turn induces a current in the secondary.
    I get the just of your first sentence, but perhaps you might want to use the words "power loss" in there somewhere. Transmitting power at higher voltage means lower currents in the wires, reducing I2R power losses in the transmission lines.
    I think you meant to use the word "induction" where you used "conduction". A changing magnetic field induces a current in a conductor.

    The basic idea of electric power generation is to convert some available source of mechanical energy (water power, coal or oil fired engines, etc.) to electrical energy via a generator employing electromagnetic induction.
    It was recognized that there were two distinct charges. An arbitrary choice was made to designate one as "positive" and the other "negative". As it turned out the choice was not ideal for typical electrical circuits given our present knowledge of what charge carriers are actually moving in a wire. By the way, the scientist involved was good old Ben Franklin.
  7. Dec 18, 2011 #6
    That's very helpful, thank you!
  8. Dec 18, 2011 #7

    Simon Bridge

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    Indeed! In fact, I hope you see that this is much much more helpful than if we'd just posted our answers.

    The downside is that you expose your work and your ideas to review and and people will point out what you did wrong. Being wrong seldom feels good - but it is essential to risk being wrong in order to get things right.
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