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

A thin plastic rod of length L with total charge +q uniformly distributed along only the outer half-length is shown in Fig. 1. The rod is rotated at a constant angular speed w rad/sec about, and perpendicular to, the z-axis. Find the magnetic field B at the pivot, perpendicular to the plane of rotation in terms of L, q and w. (Hint: View the situation as a series of concentric current loops, each with thickness dl.)

**2. Relevant equations**

No clue which equations will help with angular velocity.

**3. The attempt at a solution**

I don’t know how to go about this problem

Thanks for any help.

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