If a proton is projected in a direction perpendicular to a uniform magnetic field with velocity v and an electron is projected along the lines of force, what will happen to proton and electron?

Question

If a proton is projected in a direction perpendicular to a uniform magnetic field with velocity v and an electron is projected along the lines of force, what will happen to proton and electron? (A) The electron will travel along a circle with constant speed and the proton will move along a straight line (B) Proton will move in a circle with constant speed and there will be no effect on the motion of electron (C) There will not be any effect on the motion of electron and proton (D) The electron and proton both will follow the path of a parabola

Tardigrade Admin · Accepted Answer

For proton, v perp B and for electron v | B. So, force on proton =q( v × B )=B q v whereas, force on electron =0.

Q. If a proton is projected in a direction perpendicular to a uniform magnetic field with velocity $v$ and an electron is projected along the lines of force, what will happen to proton and electron?

The electron will travel along a circle with constant speed and the proton will move along a straight line

Proton will move in a circle with constant speed and there will be no effect on the motion of electron

There will not be any effect on the motion of electron and proton

The electron and proton both will follow the path of a parabola

For proton, $v ⊥ B$ and for electron $v ∥ B$ .
So, force on proton $= q (v \times B) = Bq v$ whereas, force on electron $= 0$ .

Q. If a proton is projected in a direction perpendicular to a uniform magnetic field with velocity v and an electron is projected along the lines of force, what will happen to proton and electron?