A spherical balloon is charged so that the potential on its surface is $40\mathrm{V}$. The balloon is now deflated to half its original radius (with no loss of charge). What is the new potential on its surface?

What is the electric potential 3.0 cm away from a $-12\text{nC}$ point charge?

A $-9.0\text{nC}$charge sits at the origin, and a $+18\text{nC}$ charge is at $x=2.0\mathrm{cm}$. At what location(s) is the potential zero?

A uniform electric field with strength $12\mathrm{V}/\mathrm{m}$ points from point A to point B, which are on the x-axis: $x_{\text{A}}=45\mathrm{m}$ and $x_{\mathrm{B}}=12\mathrm{m}$. What is the potential difference $V_{\text{A}}-V_{\mathrm{B}}$?

Metal sphere A is charged until it has a potential of $200\mathrm{V}$. Metal sphere B is initially uncharged, and has a radius twice the radius of sphere A. A small wire is used to connect spheres A and B, so that they form one continuous equipotential surface. What is the final potential on the surface of sphere B?

What are the strength and direction of the electric field 1.0 mm from (a) a proton and

A thin spherical shell with radius R_1 = 3.00 cm is concentric with a larger thin spherical shell with radius R_2 = 5.00 cm. Both shells are made of insulating material. The smaller shell has charge q_1 = +6.00 nC distributed uniformly over its surface, and the larger shell has charge q_2 = -9.00 nC distributed uniformly over its surface. Take the electric potential to be zero at an infinite distance from both shells. (a) What is the electric potential due to the two shells at the following distance from their common center: (i) r=0; (ii) r=4.00 cm; (iii) r=6.00 cm?

Two stationary point charges +3.00 nC and +2.00 nC are separated by a distance of 50.0 cm. An electron is released from rest at a point midway between the two charges and moves along the line connecting the two charges. What is the speed of the electron when it is 10.0 cm from the +3.00-nC charge?