Tv electron and earth magnetic field

AI Thread Summary
The discussion revolves around determining the direction of the force on electrons in a television tube due to the Earth's magnetic field. The electrons have an energy of 23.0 keV and move horizontally from west to east, while the vertical component of the Earth's magnetic field points downward at 57.6 T. Initially, the participant incorrectly concluded that the force direction is north using the right-hand rule, but later recognized that the negative charge of the electron reverses the force direction. After correcting the magnetic field strength to microteslas, the conclusion is that the force should actually point south. The key takeaway is the importance of considering the electron's negative charge when applying the right-hand rule.
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Homework Statement


The electrons in the beam of a television tube have an energy of 23.0 keV. The tube is oriented so that the electrons move horizontally from west to east. At the electron's latitude the vertical component of the Earth's magnetic field points down with a magnitude of 57.6 T. What is the direction of the force on the electrons due to this component of the magnetic field?


Homework Equations





The Attempt at a Solution


The options are up, down, north, south, west,east.
I chose north because B is down(middle finger), pointer finger horizontal and therefore thumb points north. Why is that wrong?
 
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57.6 T
Is an awfully strong magnetic field. The Earth's field is relatively weak.

Nevertheless, the velocity of the electron is west to east (horizontal) and the magnetic field is down (vertical) which leaves either N or S, based on

F = q (v x B), where q is the charge, v is the velocity and B is magnetic field strength.
 
With right hand rule I get north, but it is incorrect!
Sorry it should be micro teslas!
 
Last edited:
Actually shouldn't it be south because the negive from the charge of an electron flips the force the opposite direction.
 
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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