question_answer

Two parallel beams of protons and electrons, carrying equal currents are fixed at a separation d. The protons and electrons move in opposite directions. P is a point on a line joining the beams, at a distance x from any one beam. The magnetic field at P is B. If B is plotted against x, which of the following best represents the resulting curve

A)                                        

B)                               

C)                                      

D)                           

Correct Answer: C

Solution :

           The magnetic field at points to the right of the proton beam acts perpendicular to the paper inwards (´). The magnetic field at points to the left of the electron beam acts perpendicular to the paper outwards (×). Magnetic field at mid-point M is zero. Magnetic field at the points closer to proton beam acts perpendicular to the paper inwards (i.e. (´)) and at the points closer to electron beam it acts outwards i.e. (×). In the given options graph  satisfies all the conditions.