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 at the same distance. The magnetic field at P is :

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 current

Correct Answer: B

Solution :

 Let XY be a straight conductor carrying current \[i\]in the direction from X to Y. Magnetic field at P at a distance R is \[B=\frac{{{\mu }_{0}}}{2\pi }\frac{i}{R}N{{A}^{-1}}{{m}^{-1}}\] Hence, magnetic field is same at both points P and Q.