Question

A current-carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire

• A. Will exert an inward force on the circular loop
• B. Will exert an outward force on the circular loop
• C. Will exert a force on the circular loop parallel to itself
• D. Will not exert any force on the circular loop

Answer 1

Answer: (D)

According to Fleming's left hand rule, direction of magnetic field at the centre $O.$
The force on the current carrying conductor is $F=i\overrightarrow{\mathrm{dl}}\times \overrightarrow{B}$

As angle between $dl$ and B is zero
$F=0$
The straight wire will not exert any force on the circular loop.