Magnetic Field and Force (in a solenoid)

[physgrl]

Homework Statement

A 200-turn solenoid is 20.0 cm long and carries a current of 3.25 A. Find the magnetic field. Find the force exerted on a 15.0 µC charged particle moving at 1050 m/s through the interior of the solenoid, at an angle of 11.5° relative to the solenoid’s axis.

Homework Equations

r=mv/qB
torque=IABn (n=turns)
B=(μ_o/2π)*I/r
F=ILBsin(θ)
F=qvBsin(θ)

The Attempt at a Solution

n=200
l=.2m
I=3.25A

If I want to use torque=IABn to find B I need torque and I do not know how to find it with the length only. The second part I understand once I find the Magnetic Field, but I don't get how to find it with the info given.

the answer key says: B=4.08 x 10-3 T and F=1.28 x 10-5 N

 

[I like Serena]

Homework Statement

A 200-turn solenoid is 20.0 cm long and carries a current of 3.25 A. Find the magnetic field. Find the force exerted on a 15.0 µC charged particle moving at 1050 m/s through the interior of the solenoid, at an angle of 11.5° relative to the solenoid’s axis.

Homework Equations

r=mv/qB
torque=IABn (n=turns)
B=(μ_o/2π)*I/r
F=ILBsin(θ)
F=qvBsin(θ)

The Attempt at a Solution

n=200
l=.2m
I=3.25A

If I want to use torque=IABn to find B I need torque and I do not know how to find it with the length only. The second part I understand once I find the Magnetic Field, but I don't get how to find it with the info given.

the answer key says: B=4.08 x 10-3 T and F=1.28 x 10-5 N

Hi!

I think you need an extra formula.
The magnetic field inside a long solenoid is given by:
$$B=\mu_0 {n I \over \mathcal{l}}$$
as you can see on wiki: http://en.wikipedia.org/wiki/Solenoid

 

[physgrl]

Thanks!