Why Do Electrons Move in Spiral Trajectories Within a Magnetic Field?

AI Thread Summary
Electrons move in spiral trajectories within a magnetic field due to the Lorentz force, which acts perpendicular to their velocity and the magnetic field direction. This force causes the electron to curve while also allowing it to continue moving forward, resulting in a helical path. The Right Hand Rule helps visualize the direction of the force acting on the charged particle. The discussion highlights a common confusion among students regarding the nature of electron movement in magnetic fields. Ultimately, the participants reached an understanding of the concept without needing further clarification.
S. Hardt
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Hello I do not understand one of the problems in my SAT Physics book.

Homework Statement



The subsequent path of the electron is...
.
the answer for this given by the book is : Spiral or Helix
(It does not exist any picture in the book to this question.)

The explanation the book gives for this answer is:
The electron will orbit a magnetic field line but will also continue to move towards the bottom of the page , spiraling downwards.

My question for this is Why is it moving that way? There is no explanation given.This question is out of the SAT Subject Test: Physics from Kaplan.

It would be nice to get an answer soon.
I am studying SAT Physics in a Club, so we all have got the same problem with this.
 
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Ah okay I figured out half of it... there was a picture...
The force applied on the proton is according to the Right hand rule into the page.

So the question left is only: why does a charged particle moves in a spiral into the page and not in a line (of course not in the beginning but after the direction changed).
 
We figured out the answer so there is no reply needed anymore
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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