What needs to be emphasized in this step when reading?
"Turn the two-bottle assembly over, and place the assembly on a table with the filled bottle on top. Watch the water slowly drip down into the lower bottle Now, rapidly rotate the bottles in a horizontal circle a few times. Observe the formation of a funnel-shaped vortex..."

a.
rapidly rotate the bottles in a horizontal circle
c.
both A and B
b.
Watch the water
d.
neither A nor B

Athin nonconducting rod with a uniform distribution of positive charge q is bent into a circle of radius r. the central perpendicular axis through the ring is a z-axis, with the origin at the center of the ring. a) what is the magnitude of the electric field due to the rod at z = 0? n/c (b) what is the magnitude of the electric field due to the rod at z = infinity? n/c (c) in terms of r, at what positive value of z is that magnitude maximum? r (d) if r = 4.00 cm and q = 9.00 µc, what is the maximum magnitude? n/c