Why Is the Potential Zero on the Surface of a Conducting Sphere in an E-Field?

[sachi]

I've solved an electrostatics problem where we have to find the surface charge density on a conducting sphere in a previously uniform E-Field, but I had to assume that V=0 on the surface of the cylinder, and I'm not sure why this is the case. I know that E=0 inside, so the potential should be constant, but I don't see why it should be zero (is this an extra assumption, or is there something else I'm missing?)
thanks for your help

Sachi

 

[berkeman]

The potential "V" is relative to something. You can call the baseline V=0 anywhere in a field. Probably it was specified as V=0 on the surface of the sphere for ease of computation.