Question

just need to knownwhat letter it is

2. You want to build a solenoid by winding a thin wire around a tube with a diameter of 8.00 cm. You want to be able to store 5.00 J of energy in the solenoid when a current of 1.50 A runs through it. If you wind the wire so that you end up with a coil (or loop) density of 4 coils/min, how long must the solenoid be? a) 98.9 m b) 2.52x10m c) 4.44 m d) 44.0 m e) 4.00 cm

Answer 1

Energy stored in solenoid U = 0.5 B^2*Area*Length/u0 where symbols have usual meanings and

B is magnetic field = u0ni = 4pi*10^-7*4e3*1.5 = 0.00754 T

Energy stored in solenoid U = 0.5 B^2*Area*Length/u0

5 = 0.5*0.00754^2*pi*0.04^2*L/[4pi*10^-7]

L = 5*4pi*10^-7/[0.5*0.00754^2*pi*0.04^2]

= 44 m

option d answer