PQ is a current carrying conductor in the plane of the paper as shown in the figure below.

(i) Find the directions of the magnetic fields produced by it at points R and S?
(ii) Given `r_(1)gt r_(2)` , where will the strength of the magnetic field be larger? Give reasons
(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?
(iv) Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor.

Explanation

(i) The magnetic field lines produced is into the plane of the paper at R and out of it at S. (ii) Field at S `gt` Field at P Magnetic field strength for a straight current carrying
conductor is inversely proportional to the distance from the wire. (iii) The current will be going from top to bottom in the wire shown and the magnetic field lines are now in the clockwise direction on the plane which is perpendicular to the wire carrying current. (iv) Right hand thumb rule. The thumb is aligned to the direction of the current and the direction in which the fingers are wrapped around the wire will give the direction of the magnetic field.