1. The problem statement, all variables and given/known data Inside evenly charged (with charge Q < 0) sphere with radius R is evenly charged sphere with potential equal to potential in infinity and radius R/2. Both sphere are concentric. From internal sphere, tangentially to it fly out electron (with charge e < 0). What is minimal initial kinetic energy of the electron E so it can reach external sphere? Electron speed is much smaller than speed of light. 2. Relevant equations 3. The attempt at a solution External sphere does not have effect on electron because electric field inside a sphere is zero (Gauss's law), am I right? Potential in infinity is equal to zero so in inital moment charge on internal sphere is equal to zero. After the electron fly out of it its going to have charge equal to e (e > 0) and therefore it has effect on electron. My question is whether or not this new charge induces additional charges on external sphere and those additional charges have effect on electron?