23 Homework Problems

  1. Find the magnitudes of the forces F1 and F2 and that add to give the total force Ftotal shown above. This may be done either graphically or by using trigonometry.
  2. Suppose you walk 17.0m straight west and then 23.0m straight south. How far are you from your starting point, and what is the compass direction of a line connecting your starting point to your final position?
  3. To start a car engine, the car battery moves 3.76×1021 electrons through the starter motor. How many coulombs of charge were moved?
  4. A certain lightning bolt moves 35.8 C of charge. How many fundamental units of charge |qe| is this?
  5. Electrically neutral objects can exert a gravitational force on each other, but they cannot exert an electrical force on each other.
  6. What is the magnitude of the force exerted on a 4.49 C charge by a 310.24 N/C electric field that points due east?
  7. Find the direction and magnitude of an electric field that exerts a 9×10−17 N westward force on an electron.
  8. Calculate the initial (from rest) acceleration of a proton in a 3.09×106 N/C electric field (such as created by a research Van de Graaff).
  9. Suppose there is a single electron a set distance from a point charge Q, which quantities does the electric field experienced by the electron depend on?
  10. Calculate the magnitude of the electric field 8.41 m from a point charge of 8.92 mC (such as found on the terminal of a Van de Graaff).
  11. What magnitude point charge creates a 15947.46 N/C electric field at a distance of 0.513 m? How large is the field at 18.85 m?
  12. Below you see an unknown charge generating an electric field. Also indicated are two empty regions of space “A” and “B.” Which of the following statements are true from this picture of field lines?
  13. A lightning bolt strikes a tree, moving 27 C of charge through a potential difference of 1.10×102 MV. What energy was dissipated?
  14. An evacuated tube uses an accelerating voltage of 41 kV to accelerate electrons to hit a copper plate and produce x rays. What would be the final speed of such an electron?
  15. What is the potential 52.92 pm from a proton (the average distance between the proton and electron in a hydrogen atom)?
  16. A research Van de Graaff generator has a 2.01-m-diameter metal sphere with a charge of 5.25 mC on it. What is the potential near its surface?
  17. Electric field lines are always___________.
  18. Electric field lines ____________.
  19. Which of the following are units of electric field?
  20. Membrane walls of living cells have surprisingly large electric fields across them due to separation of ions. What is the voltage across an 8.00 nmthick membrane if the electric field strength across it is 5.25 MV/m? You may assume a uniform electric field.
  21. The electric field strength between two parallel conducting plates separated by 6.4 cm is 7.0 ×104 V/m. What is the potential difference between the plates? The plate with the lowest potential is taken to be at zero volts. What is the potential 1.0 cm from that plate? 
  22. Find the maximum potential difference between two parallel conducting plates separated by 0.55 cm of air, given the maximum sustainable electric field strength in air to be 3.00 MV/m.


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Physics 132: What is an Electron? What is Light? by Roger Hinrichs, Paul Peter Urone, Paul Flowers, Edward J. Neth, William R. Robinson, Klaus Theopold, Richard Langley, Julianne Zedalis, John Eggebrecht, and E.F. Redish is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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