Review Questions: Chapter 33
#1-20
1. What is meant by the expression action at a distance? It is the
interaction between things physically far apart.
2. How does the concept of a field eliminate the idea of action at a
distance? There is actual “contact” between thing and field.
3. How are a gravitational field and an electric field similar? Both are means
of exerting forces.
4. Why is an electric field considered a vector quantity? It has magnitude
and direction.
5. What are electric field lines? They are lines depicting the E field.
How do electric field line directions compare with the direction of the
force that acts on a positive test charge in the same region? They are
the same.
6. How is the strength of an electric field indicated with field lines? Closer
lines = stronger field. Further apart = weaker field.
7. How do the electric field lines appear when the field has the same
strength at all points in a region? The lines are parallel and equally spaced
between the two parallel plates.
8. Why are occupants inside a car struck by lightning safe? Charge is on
the outside and the field inside cancels to zero. All forces cancel.
9. What is the size of the electric field inside any charged conductor? The
E field inside any charged conductor is zero. The field inside cancels to
zero.
10. Can gravity be shielded? No. Gravity acts in only one direction. It is only
attractive, there is no repulsive or negatives to cancel out.
11. What is the relationship between the amount of work you do on an object
and its potential energy? Work = PE
12. How can the electric potential energy of a charged particle in an electric
field be increased? You can increase the electric potential energy by
doing work on it against an electric field.
13. What will happen to the electric potential energy of a charged particle in
an electric field when the particle is released and free to move? The PE
will convert into KE. Energy of motion.
14. Clearly distinguish between electric potential energy and electric
potential. Electric potential = electric PE/charge
15. If you do more work to move more charge a certain distance against an
electric field, and increase the electric potential energy as a result, why
do you not also increase the electric potential? There is more J per more
C. You do more work on more charge. j/c = J/C = same voltage
16. The SI unit for electric potential energy is the joule. What is the SI
unit for electric potential? V = volt = 1 Joule/coulomb
17. Charge must be present at a location in order for there to be electric
potential energy. Must charge also be present at a location for there to
be electric potential. No, electric potential = PE/charge as if a test
charge were present. Independent of charge.
18. How can electric potential be high when electric potential energy is
relatively low? Ratio can be high when charge is small.
19. How does the amount of charge on the inside surface of the sphere of a
charged Van de Graaff generator compare with the amount of the
outside? None on the inside, all charge repels to outside.
20. How much voltage can be built up on the Van de Graaff generator of 1 m
radius before electrical discharge occurs through the air? About 3
million volts.