Physics! Confused about direction of magnetic field.

Test Preparation AP Test Preparation
1

<li>a proton due east in a region that contains only a magnetic field experiences a vertically upaward force away from the surface of the earth. What is the direction of the magnetic field</li>
</ol>

<p>A.) north B.) East C.) South D.) West E.) Down</p>

<li>An electron traveling north enters a region that contains a uniform magnetic field that points due east. In which direction will the electron be deflected?
A.) north B.) East C.) South D.) West E.) Down</li>
</ol>

<p>Which way is North? Is that the sky? Please help me on these. The right-hand rule is hard to do without knowing which way is north, south, east, west, and down?</p>

2

<p>North is basically..erm....Yeah the "sky" i guess..
Upwards is basically into the page
Down is out of the page..
downwards is out of the page
east is east, right ( i think u know that)</p>

<p>west is left</p>

<p>correct me if i am wrong..</p>

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<p>Where is the page located? Is it lying flat on the table or taped to a wall?</p>

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<p>Could u clarify Xylem101...still confused</p>

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<p>Correct me if I'm wrong, but one can think of the compass as an XY plane, and accordingly assume east to be right(+x); west, left(-x); north, up(+y); and south, down(-y). Away from the earth's surface is just +z, and into the earth's surface should be -z. Use q*vXB* for great justice.
And don't forget that electrons are negatively charged and protons are positively charged, and factor this in.</p>

6

<p>or just use the RH rule (or LH for e-)</p>

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<p>When you are in the testing center, you do not need to know which way is north, east, south, or west? Just pick an arbitrary direction and use the right hand rule. North, south, east, and west are almost always in the plane of the page (unless stated otherwise) . I use the VBF (Very Bad Finger) rule - basically the same thing, but a little more comfortable when you are trying to twist your hand in different directions. Also, it doesn't matter where the paper is, you are looking for a direction relative to the magnetic field. </p>

<p>... I don't think I made any sense... oh well</p>

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<p>The page basically means INSIDE, Like when i say INTO the page im mean positive Z (or negative Z, depends how u define Z) basically anything with the page in it (into the page, out of the page) is the Z axis</p>

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<p>Draw yourself a quick diagram on your paper, labelling it north-east-west-south, like on a 2D map. Just remember that the Rt Hand Rule can also mean stuff comes out of the page, or also go into the page. This is not north or south, but rather, in and out. Also remember that you have to reverse the Rt Hand Rule if you're trying to find the force on an electron.</p>