[" Two coaxial solenoids of different radii carry current I in the same direction.Let "vec F_(1)" be the magnetic "],[" force on the inner solenoid due to the outer one and "vec F_(2)" be the magnetic force on the outer solenoid id "],[" due to the inner one.Then: "],[[" (1) "vec F_(1)=vec F_(2)=0],[" (2) "vec F_(1)=vec F_(2)=0],[" (2) "vec F_(1)=vec F_(2)" radially inwards and "vec F_(2)" is radially outwards "],[" (3) "vec F_(1)" is radially inwards and "vec F_(2)=0],[" (4) "vec F_(1)" is radially outwards and "vec F_(2)=0]]