Wikipremed Physics Flashcard error? Card #365 - Magnetism

[inasensegone]

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I came across this problem (image below as well), and I got it correct, but only because I didn't look at the experiment set-up very closely. Essentially this is like a Mass spectrometer question, where E must equal B to prevent deflection. I think there is an error with the problem though. (It seems like the terminals on the Vc-circuit should be reversed.)

Here is the problem: the solenoid orientation and circuit setup (Vc) seem to indicate that the magnetic field would point out of the page, because the current travels in a helical fashion out of the page through the solenoid. If the magnetic field travels out of the page, then it would deflect the electron upward instead of downward. The electric field already attracts the electron upward, so this cannot be.

Side note: Wikipremed is freaking awesome for physics review.

 

[scrub2scrubs]

For some reason when i do the right hand rule with the way that it is set up, I get thay the magnetic force points into the page. Am I doing it wrong?

 

[brood910]

It took me a while to understand the picture lol.

As far as I understood the picture correctly, current (cathode to anode) is going clockwise. That means, using your right hand rule, your thumb should be pointing into the page.

 

[inasensegone]

For some reason when i do the right hand rule with the way that it is set up, I get thay the magnetic force points into the page. Am I doing it wrong?

It took me a while to understand the picture lol.

As far as I understood the picture correctly, current (cathode to anode) is going clockwise. That means, using your right hand rule, your thumb should be pointing into the page.

OMG... you guys are correct ... I was misled by TBR's diagram of a solenoid (which is still correct). I forgot to apply the direction of the magnetic field when determining the rotation of current! I think I need a study break. Good thing I'm going to work right now =/

Thanks you guys!

BTW, here is TBR's solenoid diagram that I misinterpreted: