Biot-Savart Law: Biot-Savart law was discovered in 1820 by two physicists Jeans-Baptiste Biot and Felix Savart. According to this law: The magnetic field is directly proportional to the length of the current element. $dB \propto dl \qquad (1)$ The magnetic field is directly proportional to the current flowing in the conductor. $dB \propto i \qquad (2)$ The magnetic field is inversely proportional to the square of the distance between length of the current element $dl$ and point $P$ (This is that point where the magnetic field has to calculate). $dB \propto \frac{1}{r^{2}} \qquad (3)$ The magnetic field is directly proportional to the angle of sine. This angle is the angle between the length of the current element $dl$ and the line joining to the length of the current element $dl$ and point $P$. $dB \propto sin\theta \qquad (4)$
(The Advance Learning Institute of Physics and Technology)