A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is

(a) towards south                  (b) towards east

(c) downward                        (d) upward





Explanation - Since the particle deflects towards North,

The force is in towards North


Now, if positively charged particle moves towards West, 

So, current is towards West


Applying Fleming’s left hand rule,

Taking the forefinger, middle finger and thumb of the left hand in mutually perpendicular direction

  • Pointing thumb towards north direction (direction of force)
  • Middle-finger towards west direction (direction of current)
  • We get that the direction of magnetic field is upwards . (outside, towards us)



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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo