Physics - Magnetism Question with Solution | TestHub

If $\theta =0^{\circ }$, the charged particle is projected along $x$-axis, due to magnetic field, $\vec{B}$ the charged particle will tend to move in a circular path in $y-z$ plane but due to force of electric field $\vec{E}$, the particle will move in a helical path with increasing pitch. Hence options (A) and (B) are wrong. If $\theta =10^{\circ }$, we can resolve velocity into two rectangular components. One along $x$-axis $\left(v\cos 10^{\circ }\right)$ and one along $y$-axis $\left(v\sin 10^{\circ }\right)$. Due to $v\cos 10^{\circ }$, the particle will move in circular path and due to $v\sin 10^{\circ }$ plus the force due to electric field, the particle will undergo helical motion with its pitch increasing. If $\theta =90^{\circ }$, the charge is moving along the magnetic field. Therefore the force due to magnetic field is zero. But the force due to electric field will accelerate the particle along $y$-axis.