A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E → and B → represent the electric and magnetic fields respectively, then the region of space may have : (A) E = 0 , B = 0 ; (B) E = 0 , B ≠ 0 ; (C) E ≠ 0 , B = 0 ; (D) E ≠ 0 , B ≠ 0 Choose the most appropriate answer from the options given below :

Step-by-step solution

Net force on proton inside an electric and a magnetic field is given by F → e + F → m = q E → + q v → × B → . . . 1 If both E → and B → are zero, then F → e and F → m both are zero. Hence, velocity may remain constant. Therefore, option (A) is correct. If E = 0 , B ≠ 0 , but velocity is parallel or antiparallel to the magnetic field, then also F → e and F → m both are zero. Hence, option (B) is also correct. If E ≠ 0 , B ≠ 0 , but F → e + F → m = 0 , then also velocity may remain constant. Thus, option (D) is also