An electron travels at a speed of 3.58x10^6 m/s horizontally to the east. If it travels in a magnetic field of 1.3 T directed vertically upward, determine the magnitude and direction of the magnetic force exerted on the electron.

Question

anonymous · Answer

qvB is the magnitude...
direction you find from the right hand rule...
fingers point along v
rotate your hand so you can curl your fingers to point up
your thumb then points in the direction of the force

anonymous · Answer

and don't forget cross vector identity

anonymous · Answer

@gerryliyana  tell us about cross vector identity, why don't you.

anonymous · Answer

I don't know what cross vector identity is... What do I cross?

anonymous · Answer

I wouldn't worry about it.  Master the right hand rule.

ghazi · Answer

$$v*B$$ direction of this will give you the direction of motion of electron

anonymous · Answer

to the left?

ghazi · Answer

i think perpendicular to v and B  ...you can figure that out

anonymous · Answer

Yeah, I got to the left. v *b.

ghazi · Answer

no, i think it's incorrect

ghazi · Answer

|dw:1350907553942:dw| look at this ...motion in the perpendicular direction of v and B plane

anonymous · Answer

Oh.. So it's up?

ghazi · Answer

it's not up, already your magnetic field is upwards..it's outta that plane

anonymous · Answer

Oh got you!

anonymous · Answer

so which direction @sexygal  ?

anonymous · Answer

out of the page.

ghazi · Answer

|dw:1350908094962:dw| remember it could be in negative direction too which means in to the page ..be careful

anonymous · Answer

Oh yeah electrons are negative, into the page.

anonymous · Answer

take your note pad and draw a little axes on it  labeled E N W S    E should be the +x direction.
put the pad on your lap.  draw an arrow pointing east.  that's velocity.  lay your right hand on the pad so your fingers point along the arrow (East)...

anonymous · Answer

now rotate your hand so that you can curl or fold or point your fingers upwards...

anonymous · Answer

which way does your thumb point?

anonymous · Answer

out of the page

anonymous · Answer

upwards you mean?

anonymous · Answer

yeah.

anonymous · Answer

not possible...

anonymous · Answer

try again, follow the steps.

anonymous · Answer

Down.

anonymous · Answer

South.

anonymous · Answer

so the force is south... IF the quantity qvB is positive...  if it's negative, as it happens to be in this case, (because, as you pointed out, q is negative) then you reverse the direction 180 degrees... so South -> North.

anonymous · Answer

the force on the electron points North.

anonymous · Answer

So the magnitude is 4.24 X10^-24. and the direction is north?