Question

An infinitely long straight conductor is fixed and carries a current $I_1$. Another movable straight wire $\text{CD}$ (of finite length ) carrying a current $I_2$ is held perpendicular to it and released. Neglecting its weight, which of the statement is correct.

• A. Wire $\text{CD}$ moves upward, parallel to itself
• B. Wire $\text{CD}$ moves downward, paralllel to itself.
• C. Wire $\text{CD}$ moves upwards and turns clockwise at the same time
• D. Wire $\text{CD}$ moves upwards and turns anticlockwise at the same time

Answer 1

The correct option is C Wire $\text{CD}$ moves upwards and turns clockwise at the same time

Clearly, the wire $\text{CD}$ is situated in a non-uniform magnetic field over its length.

The magnitude of field is maximum at end $\text{C}$ and minimum at the end $\text{D}$.

Hence, the magnitude of force will go on decreasing from $\text{C}$ to $\text{D}$.

Hence, the wire $\text{CD}$ will move upwards. But, due to unsmmetrical distribution of force, the wire will also rotate in clockwise direction.