Which of the following is NOT a similarity between the Biot-Savart law and Coulomb’s law?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → The electrostatic field is produced by a scalar source, the electric charge.
Option (1) The electrostatic field is produced by a scalar source, the electric charge. — Not a similarity. This is a difference between the two laws. The source of the magnetic field is the vector current element \( I\,d\vec{l} \), while the source of the electrostatic field is the scalar charge.
Option (2) Both fields depend inversely on the square of the distance from the source. — A similarity. The field of a charge and the field of a current element both fall as \( 1/r^{2} \), so both are long range.
Option (3) Both fields are linear in their sources. — A similarity. Doubling the charge doubles the electrostatic field, and doubling \( I\,d\vec{l} \) doubles the magnetic field.
Option (4) The principle of superposition applies to both fields. — A similarity. The total field of several charges, or of several current elements, is the vector sum of the fields of the individual sources.
NCERT (2026-27):
Magnetic Field Due to a Current Element, Biot-Savart Law – “The Biot-Savart law for the magnetic field has certain similarities, as well as, differences with the Coulomb’s law for the electrostatic field. Some of these are: … (ii) The electrostatic field is produced by a scalar source, namely, the electric charge. The magnetic field is produced by a vector source I dl.”