7.1 Electric Potential Energy

If Q has a mass of $4.00 \mu \text{g} ,$ what is the speed of Q at $r_{2} ?$

What is the potential energy of Q relative to the zero reference at infinity at $r_{2}$ in the above example?

Is the electrical potential energy of two point charges positive or negative if the charges are of the same sign? Opposite signs? How does this relate to the work necessary to bring the charges into proximity from infinity?

Would electric potential energy be meaningful if the electric field were not conservative?

Does the order in which we assemble a system of point charges affect the total work done?

Consider a charge $Q_{1} \left(+ 5.0 \mu \text{C}\right)$ fixed at a site with another charge $Q_{2}$ (charge $+ 3.0 \mu \text{C}$, mass $6.0 \mu \text{g} \left.\right)$ moving in the neighboring space. (a) Evaluate the potential energy of $Q_{2}$ when it is 4.0 cm from $Q_{1} .$ (b) If $Q_{2}$ starts from rest from a point 4.0 cm from $Q_{1} ,$ what will be its speed when it is 8.0 cm from $Q_{1}$? (Note: $Q_{1}$ is held fixed in its place.)

To form a hydrogen atom, a proton is fixed at a point and an electron is brought from far away to a distance of $0.529 \times 10^{−10} \text{m},$ the average distance between proton and electron in a hydrogen atom. How much work is done?