Question:
The external surface of a short vertical segment of plastic pipe is hidden from view by wire wrapped around the pipe. Current flows clockwise as out looked from above in the wire. What is the path of the magnetic field produced by the wire at a point inside the pipe?
Answer:
We conclude the direction of the magnetic field by means of the right hand rule for something curly something straight. We twist the fingers of our right hand around in the direction of the current. The thumb after that points downward so the direction of the magnetic field is downward.