Sign Conventions Electrical Potential E avg =  V/d  V = E d It would be logical to set up a sign convention where  V is + when a + test charge gains potential and negative when it moves with the field Moving against the lines would be a gain of potential (like compressing a spring)  V = E d + + x This doesn’t work!! So we say instead E avg =  V/d  V = E d Moving in an electric field strength cause changes in potential

What motion will cause no change in potential? What motion will cause the largest change in potential?

Sign Conventions Electrical Potential

V = kQ/r is the potential in that region of space a distance r from a charge charge Q, assuming that the potential is zero at ____________. When is V + ? Neg?

Consider a positively charge metal sphere? How will the charge distribute within the sphere? How will potential change as you approach the sphere from the outside? Inside the sphere? As you go away from the sphere? So inside a charged sphere V is always ______  V is always _______ and E is always _________

Electrons will rearrange themselves on any conductor until the potential at all points on the surface is ______________ The electric field inside this dome is ____. The potential inside this dome is _______ The change in potential inside this dome is _____ The inside of such a 3d metal conductor with no field is called a “Faraday Cage”. Electric fields cannot enter.