# Find Current in a Solenoid Given Magnetic Field and Velocity

**1. The problem statement, all variables and given/known data**

An electron circles at a speed of 8510 m/s in a

radius of 2.42 cm in a solenoid. The magnetic

ﬁeld of the solenoid is perpendicular to the

plane of the electrons path. Find the current in the solenoid if it has

23.3 turns/cm.

Answer in units of mA

**2. Relevant equations**

I think you can use B=uIN

I=B/(uN)

u is the universal vacuum permittivity constant, n is the number of turns

**3. The attempt at a solution**

I already calculated force to be 2e-6.

There are 56.386 turns total because 23.3*2.42

so I got 2e-6/(4pi*10^-7*56.386)=0.02822

so 28.22 mA

I punched this in and it was wrong.

Did I do something weird?

http://ift.tt/1lue41h

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