question_answer

A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west of it at the same distance. The magnetic field at P is (Consider earth magnetic field also) -

A) Greater than at Q

B) Same as at Q                      

C) less than at Q                        

D) Greater or less than at Q depending upon the strength of the current

Correct Answer: A

Solution :

\[{{B}_{W}}=B\] due to wire

\[{{B}_{E}}=\]Magnetic field due to earth

\[{{B}_{Net\,\,Q}}={{B}_{W}}-{{B}_{E}}\]

\[{{B}_{Net\,\,P}}={{B}_{W}}+{{B}_{E}}\]

\[\therefore \,\,\,\,{{B}_{Net\,\,P}}>{{B}_{Net\,\,Q}}\]