A very long insulating cylinder of charge of radius 2.50 cm carries a uniform linear density of 15.0 nC/m. (a) Use Gauss’s law to find an expression for the electric field a short distance r from the cylinder. (b) If you put one probe of a voltmeter at the surface, how far from the surface must the other probe be placed so that the voltmeter reads 175

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