# Solenoid Problem

1. Sep 29, 2006

### Alt+F4

(a) How many turns of wire would be on a solenoid carrying a current 4.9 A if the solenoid is 20 cm in diameter, 248 cm long, and the field at the center is 3.3 × 10-3 T?

The magnetic field of a solenoid is the permeability of free space times the number of turns per unit length times the current.

Now How do i find the Number of turns per unit length, Is it Length/Diameter * The field of Center? Thanks
and i know n = N/L so how do i find that

Last edited: Sep 29, 2006
2. Sep 29, 2006

### Alt+F4

Okay so Basically i tried to use N = 2RB/ (uoI) to get the answer but that does not work

3. Sep 29, 2006

### Chi Meson

The diameter of a long solenoid does not matter. The magnetic field (ideally) is B=(uo)nI . Solve for n .

4. Sep 29, 2006

thanks alot