For a positively charged particle moving x-y plane initially along x-axis

Question

For a positively charged particle moving in a x-y plane initially along the x-axis, there is a sudden change in its path due to the presence of electric and/or magnetic fields beyond P. The curved path is shown in the x-y plane and is found to be non-circular.Which one of the following combinations is possible?

(a) E = 0; B =bi + ck  

(b) E = ai; B =ck + ai  

(c) E = 0; B =cj + bk

(d) E = ai; B =ck + bj 

Answer 1

As the curved path is confined to the XY plane,  the component of magnetic field effective in  deflecting the particle is the Z-component only.  The other component should be the X-component since the X-component cannot deflect the charged particle proceeding along the X-direction. There has to be an electric field since the path of the particle is non-circular. All these conditions are satisfied by option (b).