Question

Which of the following pairs of coils has zero coupling constant?

• A.

  

• B.

  

• C.

  

• D. All the above option

Answer 1

The correct option is B

Coupling Constant:

1. It is denoted by $L$.
2. It can be written as $L=\frac{\text{Flux}}{\text{Current in coil}-1}$.
3. Option B is correct because the field produced by Coil $C_1$ in this pair is parallel to the surface of coil $C_2$, so the flux coupled with $C_2$ will be zero, resulting in a zero coupling constant.
4. A coupling constant (also known as an interaction constant) is a field theory parameter that determines the relative strength of interaction between particles or fields.
5. we can note here that if the area vector $\hat{\mathrm{A}}$ of loop $C_2$is perpendicular to the direction of the magnetic field produced by the loop $C_1$ ( which is given by the right-hand thumb rule), then, the magnetic flux through loop $C_2$ will be zero which means the coil is not flux-linked.
   This is the same case as option B in which loop$C_1$ and loop $C_2$are perpendicular to each other.

Hence, option(B) is correct.