Shock Value B

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sean9keenan
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Re: Shock Value B

Post by sean9keenan »

space scientist wrote:
sean9keenan wrote:I do believe that the rules say you dont need to know much about inductors as they apply in circuits, but you do need to know about electromagnets. For instance you probably won't be asked to solve for the current through an inductor as a function of time. They can definitely ask you about the strength of the magnetic field or to draw the field lines.

I would recommend reading this: http://hyperphysics.phy-astr.gsu.edu/hb ... lemag.html It covers a lot of the material you'd need! You might also want to do some reading up about how toroids are used as cores of electromagnets
Please may you explain some of the information in simpler terms than what on the website.
Anything in particular? Perhaps try clicking on the blue words you don't understand or looking them up on wikipedia.
JSGandora wrote:Could you tell me more about...
sean9keenan wrote:...the principles behind the fast change in voltage inducing a current and creating a higher voltage across the spark plug...
please? You've caught my interest. :)
Try looking here : http://en.wikipedia.org/wiki/Ignition_coil

This device works on the same general principle that a transformer does, which uses a changing current to induce a changing magnetic field, which then induces a changing current on the other side of the magnet. This works great for AC when the current is constantly changing but not for DC. However, when you first hook up a DC battery it does jump in current from, 0 to whatever it is, so it can infact "induce" or create a current on the other side of the transformer for a short period of time, which is all you need in order to make a spark

This is the idea of how a transformer works: http://en.wikipedia.org/wiki/Transforme ... principles
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Re: Shock Value B

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sean9keenan, what I want the most help with would be information finding the polarity of an electromagnet. Please may you also explain the differences in the systems of measurement for magnetic fields.
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Re: Shock Value B

Post by Nylus22 »

Taft middle school is gonna win at state!!! :ugeek:
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Re: Shock Value B

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Really? I imagine it must be disappointing to the other teams to already know they can't win, since your victory is set in stone.
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Re: Shock Value B

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space scientist wrote:sean9keenan, what I want the most help with would be information finding the polarity of an electromagnet. Please may you also explain the differences in the systems of measurement for magnetic fields.
The polarity of an electromagnet depends entirely on which direction the current through the wires is going see:
Image

A common way of remembering this convention is to use the "right hand rule" where your fingers curl in the direction of the current, and your thumb points in the direction of the magnetic field. This works because the current through a wire directly causes a magnetic field that looks like this:
Image

And the magnetic fields sum for the entire length of the wire since it's wrapped in coil, think about it, the magnetic field always points up in the center of the circle of a wire.

As to the systems of measurements of magnetic fields what exactly are you curious about?

http://hyperphysics.phy-astr.gsu.edu/hb ... ie.html#c1

Might provide some good reading to start out with, other then that,

http://en.wikipedia.org/wiki/SI_electromagnetism_units

might help as well, unfortunately a lot of units that involve "magnetism" can actually represent different things, and might not just be simple unit conversions. Sort of like the conversion between weight and mass, or current and charge, their is a relationship between the two, but it depends on the physical scenerio.

Hope that helps, sorry for the late response,

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Re: Shock Value B

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Does "direction of current" refer to electron flow notation or conventional flow notation?
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Re: Shock Value B

Post by sean9keenan »

space scientist wrote:Does "direction of current" refer to electron flow notation or conventional flow notation?
Conventional flow notation, "positive" current
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Re: Shock Value B

Post by space scientist »

Today I uploaded a Shock Value practice test onto the test exchange, and it didn't appear on the test exchange page. Is this normal, and does a moderator or administrator have to move the file onto the test exchange?

Edit: Never mind. The test and answer key got moved to the test exchange page.
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Re: Shock Value B

Post by shweta2011 »

Hi..
I was wondering if anyone could post any recent Shock Value tests? I have the state level competition coming up this SAturday

I also wanted to know if someone could explain how to find the voltage drop across a resistor?

Thanks. any help is appreciated.
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Re: Shock Value B

Post by Schrodingerscat »

shweta2011 wrote:Hi..
I was wondering if anyone could post any recent Shock Value tests? I have the state level competition coming up this SAturday

I also wanted to know if someone could explain how to find the voltage drop across a resistor?

Thanks. any help is appreciated.
Finding the voltage drop of a resistor depends on the situation which you are disscussing.
The most straightforward method would be to measure it using a voltmeter, but I am assuming that was/is/will not be an option.
The other method is if you know the resistance of the resistor and the current passing through the resistor, ohms law still applies and can be used to calculate the voltage.
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