Question

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?

Answer 1

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