Answer to Question 3

 

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A solenoid consists of 200 turns and is 5.0 cm long.  It is carrying a current of 2.0 A.  Calculate the energy density.

Calculate the number of turns per metre:

n = 200 turns 0.050 m = 4000 m-1

 

U = [4p 10-7 H m-1 (4000 m-1 )2 (2.0 A)2 ] 2 = 40 J m-3