Question #21d0f

1 Answer
Jan 30, 2016

Only possible if velocity of the charged particle is=1.907times 10^7 m//s=1.907×107m/s. Direction of vec vv must be as assumed in the solution.
It is independent of e/mem

Explanation:

This is a question related to Motion of a Charged Particle in Electric and Magnetic Field. Let us recall the applicable Lorentz Force equation

vec F=q[vecE + (vecvxxvecB)] F=q[E+(v×B)]
where qq is the charge of the particle, vecEE is the electric field, vecvv is the velocity of the charged particle and vecBB is the magnetic field.

Assumption of direction of three Vectors

Let the charged particle move in the direction given by hat xˆx, the electric field be in the hatyˆy and magnetic field be in the hatzˆz direction.

Electric field vecEE will exert force on the charge in its direction, assuming the charge qq to be positive.

The direction of the force exerted by the magnetic field is cross product of velocity and magnetic field vectors and is

hat x times hat z=-hatyˆx׈z=ˆy.
It is acting in a direction opposite to the electric field vector.
As it is required that the charge should pass through in a straight line, it implies that

Lorentz force must be zero.

0=q[|vecE|hat y - |vecv|.|vecB|haty] 0=q[Eˆyv.Bˆy]
=>|vecE|=|vecv|.|vecB|E=v.B
16728=0.000877times |vecv|16728=0.000877×v
|vecv|approx1.907times 10^7 m//sv1.907×107m/s