Q. An electron (charge $q$ coulomb) enters a magnetic field of $H\ weber/m^{2}$ with a velocity of $vm/s$ in the same direction as that of the field. The force on the electron is
A) $Hqv$ newtons in the direction of the magnetic field
B) $Hqv$ dynes in the direction of the magnetic field
C) $Hqv$ newtons at right angles to the direction of the magnetic field
D) Zero
Explanation
(d) $\overrightarrow{F} = q\left( \overrightarrow{v} \times \overrightarrow{B} \right) = 0$ as $\overrightarrow{v}$ and $\overrightarrow{B}$ are parallel
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.