Discussion Forum



1)

Two coaxial solenoids of different radii carry current I  in the same direction. Let F1 be the magnetic force on the inner solenoid due to the outer one and F2 be the magnetic force  on the outer solenoid due to the inner one, Then,


A) $F_{1}=F_{2}=0$

B) $F_{1}$ is radially inwards and $F_{2}$ is radially outwards

C) $F_{1}$ is radially inwards and $F_{2}$=0

D) $F_{1}$ is radially outwards and $F_{2}$=0

Answer:

Option A

Explanation:

Consider the two coaxial solenoids. Due to one of the solenoids magnetic field at the centre of the other can be assumed to be constant

 2622021281_m26.PNG

 Due to symmetry, forces on upper and lower part of a solenoid  will be equal and opposite and hence resultant is zero , Therefore $F_{1}$ = $F_{2}$=0