Answer:

A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each.

N = 5*400 = 2000

The diameter of the solenoid is 1.8 cm. The current carried is 8 A.

The magnetic field inside a long solenoid is properly calculated by using the cross product and maybe the right hand rule, but all that can be simplify into:

B = µ₀ * N * I / L

where

B is the magnetic field,

µ₀ = 1.25664 * 10^-6 T*m/A is the vacuum permeability,

N is the number of turns in the solenoid,

I is the electric current,

L is the length of the solenoid.

Put the values in the given formula

We get, magnetic field

B = 0.025133 T

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