TBR physics VIII question 65

[zzzcor]

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if anyone have the TBR physics book and it says

electron with greater velocity will deflect downward but when are we provided with the information about the direction of electric field or magnetic field in the cathode in the passage so that we can determine the direction? other than that the direction of two forces will be opposite

 

[whiteshadodw]

if anyone have the TBR physics book and it says

electron with greater velocity will deflect downward but when are we provided with the information about the direction of electric field or magnetic field in the cathode in the passage so that we can determine the direction? other than that the direction of two forces will be opposite

F=Eq, force on a charged object in an electric field is independent of mass or speed. just charge and the electric field.

F=qvB, force on a charged object with a velocity perpendicular to the magnetic field is not zero. but we're assuming that previously the velocity was v and that the electron did not deflect indicationed that F=0=Eq+qvB. thus when we double the velocity we get F=/=0=Eq+2v*q*b, the electron deflects and doesn't travel in a straight line. the force due to the magnetic field acting on a charged particle with a velocity becomes greater than the force due to the electric field. the force due to the electric field cancels out some of the force due to the magnetic field, but not all of it. hence its deflected.

in a real mass spec, there is a wall at the end of the capacitor with a hole in the EXACT middle to ensure that only particles travelling straight get out of the ionizer and into the analyzer.

 

[SN2ed]

Thread moved. These types of questions belong in the Study Q&A forum.

 

[zzzcor]

F=Eq, force on a charged object in an electric field is independent of mass or speed. just charge and the electric field.

F=qvB, force on a charged object with a velocity perpendicular to the magnetic field is not zero. but we're assuming that previously the velocity was v and that the electron did not deflect indicationed that F=0=Eq+qvB. thus when we double the velocity we get F=/=0=Eq+2v*q*b, the electron deflects and doesn't travel in a straight line. the force due to the magnetic field acting on a charged particle with a velocity becomes greater than the force due to the electric field. the force due to the electric field cancels out some of the force due to the magnetic field, but not all of it. hence its deflected.

in a real mass spec, there is a wall at the end of the capacitor with a hole in the EXACT middle to ensure that only particles travelling straight get out of the ionizer and into the analyzer.

Yeah I get that it will deflect more but I am just confused whether it will deflect upward or downward because the direction will depend on the orientation of magnetic field and electric field but in the passage, it doesn't mention how the field are oriented and asks which direction it will be deflected to.

 

[whiteshadodw]

Yeah I get that it will deflect more but I am just confused whether it will deflect upward or downward because the direction will depend on the orientation of magnetic field and electric field but in the passage, it doesn't mention how the field are oriented and asks which direction it will be deflected to.

i'm assuming you're talking about passage 10. in which case, you can clearly see the capacitor is labeled with the top plate being the + and the bottom being -. so the force due to the electric field on an electron points upward. since the magnetic field has to cancel out the electric field, it points downward. that's the only way you can get things to "not deflect". it tells you F=qvb, and velocity has doubled, so magnitude of magnetic field HAS to increase. but the force due to the electric field/capacitor hasn't changed at all. the force due to the electric field of the capacitor points up, the force due to the magnetic field points down. this is stated explicitly in the passage "The electric field and magnetic field are set up so that the forces on the electrons will point in opposite directions."