The inductance of a solenoid is defined to be l = î¦b/i, where î¦b is the total magnetic flux passing through the solenoid due to its own b field when a current i flows through it. show that the inductance of a solenoid is equal to l = âµon 2 la, where n is the number of turns per length, l the length, and a the cross sectional area of the solenoid. [5 marks] (2b) a 2000-turn solenoid made of aluminum wire with radius 0.370 mm has length 1.50 m and diameter 5.00 cm. show that the total resistance of the wire making up the solenoid is 20.1 â¦. [5 marks] (2c) this soleoid is connected to a 40.0 v emf through a switch. find the time constant of the resulting rl circuit, ïrl = l/r. [5 marks] (2d) find the current flowing through the solenoid when the switch is just closed, and the magnetic field in the solenoid a long time after the switch is closed. [5 marks] (2e) sketch the magnetic field inside the solenoid as a function of time after the switch is closed.