Two coaxial solenoids of different radius carry current $I$ in the same direction. $\overrightarrow {{F_1}} $ be the magnetic force on the inner solenoid due to the outer one and $\overrightarrow {{F_2}} $ be the magnetic force on the outer solenoid due to the inner one. Then :
$\overrightarrow {{F_1}} $ is radially in wards and $\overrightarrow {{F_2}} = 0$
$\overrightarrow {{F_1}} $ is radially outwards and $\overrightarrow {{F_2}} = 0$
$\overrightarrow {{F_1}} = \overrightarrow {{F_2}} = 0$
$\overrightarrow {{F_1}} $ is radially inwards and $\overrightarrow {{F_2}} $ is radially outards
