Question

The physical quantity which is measure in the unit of wb A^-1 is

• A. Self inductance
• B. Mutual inductance
• C. Magnetic flux
• D. Both (A) and (B)

Answer 1

The Correct Option is D

We are looking for the physical quantity measured in the unit of Wb A^-1. Recall that 1 Weber (Wb) is the unit of magnetic flux.

Inductance

Self-inductance ($L$) and mutual inductance ($M$) are both defined by the relationship between induced voltage and the rate of change of current. Both have units of $\text{Wb} \cdot \text{A}^{-1}$ commonly known as the Henry (H):

For Self Inductance $\mathcal{E} = -L \frac{dI}{dt} $ and thus $ L= -\frac{\mathcal{E} dt}{dI} $ which has units of Volt-second/Ampere = (Joule/Coulomb) x Second/Ampere = Joule-second/(Ampere x Coulomb)= Weber/Ampere Similarily for mutual inductance, we have $\mathcal{E} = -M \frac{dI}{dt} $ and thus $ M= -\frac{\mathcal{E} dt}{dI} $

Magnetic Flux is measured in Webers (Wb). Thus Wb A^-1 is not the unit of magnetic flux.

Therefore, the physical quantities measured in Wb A^-1 are self-inductance and mutual inductance.

The correct answer is (D) Both (A) and (B).