Unit 19: Electric Potential Energy & Voltage
Practice Problems
Note: problem difficulty is ranked using a star system.
(*) One-star problems are fundamental to the unit, and can be done relatively quickly. Use these problems to introduce yourself to the material.
(**) Two-star problems are more difficult, and require an understanding of one or two key concepts. Use these problems to test your understanding of the material.
(***) Three-star problems are the most difficult, and require some creative thinking in addition to a deep familiarity with multiple key concepts. Use these problems to challenge yourself; if you can complete one of these, you’re on your way to mastering the material.
*Q19.1) How much potential energy would a proton have if it were placed 20nm from a calcium ion?
**Q19.2) How much work would you have to do to move the proton from the previous problem 5nm closer to the calcium ion?
**Q19.3) A calcium ion and a chlorine ion are separated by 50nm. Find the electric potential at the midpoint between them.
**Q19.4) A calcium ion and a chlorine ion are separated by 50nm. Where (if anywhere) will the electric potential be 0?
**Q19.5) An electron is released from rest between a pair of charged parallel plates as shown below. Find its speed when it strikes the positive plate.
**Q19.6) An electron is shot between a pair of charged parallel plates at 1% the speed of light as shown below. Find its speed when it strikes the positive plate (as a percentage of the speed of light).
***Q19.7) An electron is placed precisely at the midpoint between two calcium ions. Is the electron at equilibrium? If so, is this equilibrium stable? In other words if the electron were perturbed slightly, would it return to the midpoint or fly off towards one of the calcium ions?