Page 290 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 23] ELECTRICITY 275

23.16. A potential difference of 100 V is applied by a battery across a pair of metal plates 5 cm apart. (a) What is the
electric field between the plates? (b) How much force does a charge of +10 −8 C experience in this field? (c)How
much kinetic energy does this charge acquire when it goes from the postive plate to the negative plate?
23.17. A charge of −2 × 10 −9 C in an electric field between two parallel metal plates 4 cm apart is acted on by a force of
10 −4 N. (a) What is the strength of the field? (b) What is the potential difference between the plates?

23.18. A proton is accelerated by a potential difference of 15,000 V. What is its kinetic energy?
23.19. A particle of charge 10 −12 C starts to move from rest in an electric field of 500 V/m. (a) What is the force on the
particle? (b) How much kinetic energy will it have when it has moved 1 cm in the field?
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23.20. When a certain 12-V storage battery is charged, a total of 10 C is transferred from one set of its electrodes to the
other set. Find the energy stored in the battery.

Answers to Multiple-Choice Questions

23.1. (a), (d) 23.8. (d)
23.2. (a) 23.9. (b)

23.3. (c) 23.10. (c)

23.4. (b) 23.11. (a)

23.5. (c) 23.12. (c)

23.6. (b) 23.13. (d)
23.7. (b) 23.14. (c)

Answers to Supplementary Problems

23.1. (a) 8 electrons (b) 10 electrons

23.2. Such a sketch shows how the magnitude and direction of the field vary in space. At a given point, the direction of
the field is given by the direction of the nearest lines of force, and the relative magnitude of the field is indicated by
how close together the lines of force are in the vicinity of the point.

23.3. By definition, a line of force represents the path a positively charged particle would follow in an electric field, and
such a particle can travel in only one direction at any point.

23.4. The force exerted by the field on the −q charge is equal and opposite to the force exerted on the +q charge, so the
rod does not move since the two forces have the same line of action.

23.5. The equal and opposite forces exerted on the charges now cause the rod to rotate until it is parallel to the electric
field.

23.6. −1.6 × 10 −10 C