दो आवेशित कण एकसमान चुंबकीय क्षेत्र B = B0k̂ में पूर्णतः विपरीत दिशाओं में एक जैसी पेचदार (helical) पथों पर चलते हैं। निम्नलिखित में से कौन सा कथन सही है?

A charged particle is released from rest in a region of space where steady and uniform electric and magnetic fields are parallel to each other. The particle will move in a:

Two very long, straight, parallel wires carry steady currents I and 2I in the same direction. The distance between the wires is d. At a certain instant, a point charge q is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity v is perpendicular to this plane. The magnitude of the magnetic force acting on the charge at this instant is: