Question

How much energy is stored in a 2.60-cm-diameter, 13.0-cm-long solenoid that has 160 turns of wire and carries a current of 0.780 A ?

Answer 1

The magnetic field inside the solenoid is constant everywhere and is given by
  
And the volume of the solenoid is
   
where, d is the diameter of the solenoid. And so, the energy stored in the solenoid is
   
   
  
   
And so, given the values,
   d = 2.60 cm = 0.026 m, N = 160 , I = 0.780 A, L = 13.0 cm = 0.13 m,
and so, we get