Question

How will the strength of the magnetic field change when the point where the magnetic field is to be determined is moved away from the straight wire carrying constant current? Justify your answer.

Answer 1

1. Magnetic field is a region, where the force of magnetism acts.
2. From Biot-Savart's law, the magnetic field is proportional to the current, inversely proportional to the square of the distance to the point from the wire and the angle between $dl$ and $r$.
3. We know that the magnetic field at a point due to a current-carrying conductor is $B=\frac{{\mu }_0}{4\pi }\frac{idl\sin \theta }{r^2}$, where ${\mu }_0$ is the permeability of free space, $i$ is current, $dl$ is change in length of the conductor, $r$ is the distance between the conductor and the point of magnetic field and $\theta$ is the angle between $dl$ and $r$.
4. The magnetic field is inversely proportional to the square of the distance of the point from the conductor. So, the magnetic field will decreases, when distance will increase. That means the strength of the magnetic field will decrease.

So, when the point moved away from the magnetic field, the strength of the magnetic field on the point will decrease.