Question

A charged particle moving at speed v enters a uniform magnetic field of strength B in a path perpendicular to the field lines.
Which of the following would cause the greatest increase in magnetic force on the particle?

• A. Doubling the speed.
• B. Decreasing the strength of the magnetic field.
• C. Tripling the charge on the particle.
• D. Entering the magnetic field in a path running parallel to the field lines.

Answer 1

The correct option is C Tripling the charge on the particle.

The magnetic force acting on the particle $F=qvB$ $(\because v\perp B)$

(A) : $v^{\prime }=2v$ $⟹F^{\prime }=q\left(2v\right)B=2F$

(C) : $q^{\prime }=3q$ $⟹F^{\prime }=\left(3q\right)vB=3F$

(B) : Decreasing the strength of magnetic field will decrease the magnetic force.

(D) : $v\parallel B$ $⟹F=0$

Hence option C is correct.