Question

SI unit of magnetic induction is _____.
A. coulomb
B. tesla
C. curie
D. none

Answer 1

Hint: In this question, students need to find out the S.I. unit of magnetic induction (B) that is magnetic flux per unit area. Mathematically, magnetic induction is given by:

\[\text{B=}\dfrac{\text{ }\!\!\Phi\!\!\text{ }}{\text{A}}\] where, Ф is magnetic flux and A is the area through which magnetic lines of force are passing.

Complete step by step answer:
When the magnetic flux is uniformly distributed over an area A, then in that case we define magnetic flux density (B), as the magnetic flux (Ф) per unit area (A).

 Magnetic induction is the measure of magnetic flux per unit area.

i.e., \[\text{B=}\dfrac{\text{ }\!\!\Phi\!\!\text{ }}{\text{A}}\] (when area A is perpendicular to magnetic flux Ф)

On the basis of this relation, the S.I. unit of magnetic flux density is given by

\[\text{1 tesla = 1}\dfrac{\text{weber}}{{{\text{m}}^{2}}}\]

Hence, the correct option is B, i.e., tesla.

Additional Information:
One tesla is equal to one weber per square meter. The unit was announced in 1960 by the General Conference on Weights and Measures and is named in the honour of Nikola Tesla.

There is one more thing to understand, that the difference between magnetic field strength H and the magnetic induction B. In practice, people almost always call B, the magnetic field, which is because the reason that the term ‘induction’ suggests an induced magnetic moment. Since an induced magnetic moment is usually not in evidence, so the term induction is felt to be confusing. That is why people call magnetic induction a magnetic field.

Note: Students should memorize the formula for basic physical quantities so that they can find out their units easily. Here coulomb is the unit of electric charge, so option A is incorrect and curie is the unit of radioactivity so option C is also incorrect.