Question

Direction of current in coil \((2)\) is opposite to direction of current in coil \((1)\) and coil \((3)\). All three coils are coaxial and equidistant coil \((1)\) and coil \((3)\) are fixed while coil \((2)\) is suspended thus able to move freely. Then –


1 2 ( 3

• A. If the direction of current in coil $2$ is same as that of coil $1$ and coil $3$ then the state of equilibrium of coil $2$ along axial direction is unstable
• B. Equilibrium state of coil $\left(2\right)$ is unstable equilibrium along axial direction
• C. Coil $\left(2\right)$ is in equilibrium
• D. Equilibrium state of coil $\left(2\right)$ is stable equilibrium along axial direction

Answer 1

Answer: (A), (C), (D)

The correct options are
A If the direction of current in coil $2$ is same as that of coil $1$ and coil $3$ then the state of equilibrium of coil $2$ along axial direction is unstable
C Coil $\left(2\right)$ is in equilibrium
D Equilibrium state of coil $\left(2\right)$ is stable equilibrium along axial direction




$\because \overrightarrow{F_{32}}=-\overrightarrow{F_{12}}$, thus the coil is in equilibrium.

If coil $\left(2\right)$ is slightly displaced in left side then $\overrightarrow{F_{12}}$ become greater than$\overrightarrow{F_{32}}$ thus coil $\left(2\right)$ go to its previous position i.e. in right side. Thus coil $\left(2\right)$ is in the stable equilibrium state along axial direction.

If the direction of current in the coil $\left(2\right)$ is in the same direction as coil $\left(1\right)\&\left(3\right)$, then $\overrightarrow{F_{12}}\ne -\overrightarrow{F_{32}}$




If coil $\left(2\right)$ is displaced in left side then $\left|\overrightarrow{F_{12}}\right|>|-\overrightarrow{F_{32}}|$, then coil will go in left side. Therefore, equilibrium is unstable.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(A\right),\left(B\right)\&\left(D\right)$ is the correct answer.