Question

AB is a current-carrying conductor in the plane of the paper as shown in the figure. What are the directions of magnetic fields produced by it at points P and Q? Given $ {r}_{1}>{r}_{2}$, where will the strength of the magnetic field be stronger?

Fig. \( 13.7 \)

Answer 1

Given data

$r_1>r_2$

Current carrying conductor

1. A current-carrying conductor produces a magnetic field around it. i.e. behaves like a magnet and exerts a force when a magnet is placed in its magnetic field.
2. Similarly, the magnetic field acts on the current-carrying conductor with an equal and opposite force.

Right-hand thumb rule

1. "If the current-carrying conductor is held in the right hand with the thumb finger-pointing in the direction of the current flow and the other fingers curled around the conductor, the curled fingers indicate the direction of the magnetic field due to the current-carrying conductor," according to the right-hand thumb rule.
2. This law merely depicts the position of the current conductor's magnetic field.
3. Demonstrating with the help of a diagram

Applying the right-hand thumb rule

1. Using the right-hand thumb rule, the magnetic field would be anti-clockwise around the current direction, as indicated in the above diagram. As a result, the magnetic field at point P would be directed into the paper plane.
2. The magnetic current would be flowing away from the plane of the paper at point Q.
3. Because the strength of the conductor is inversely related to distance from the conductor, the magnetic field is greater near the conductor and weaker as we move away from it.
4. The distance between point P and the conductor is higher than the distance between point Q and the conductor, the magnetic field near point Q is stronger than the magnetic field near point P.

Hence, the magnetic field near point Q is stronger than the magnetic field near point P.