How many turns should a 10-cm long solenoid have if it is to generate a 1.5 x 10-3 t magnetic field on 1.0 a of current?

We can answer this problem using Ampere’s Law:

Bh = μoNI

Where:

B = Magnetic Field

h = coil length

μo = permeability = 4π*10^-7 T·m/A

N = number of turns

I = current

It is given that B=0.0015T, I=1.0A, h=10 cm = 0.1m

Use Ampere's law to find # turns:

Which can be rewritten as:

N = Bh/μoI

N = (0.0015) (0.1) / (4π*10^-7) (1.0)

N = 119.4

Answer: 119.4 turns