 University Physics Volume 2

# Conceptual Questions

University Physics Volume 2Conceptual Questions

### 7.1Electric Potential Energy

1 .

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

2 .

Why do we need to be careful about work done on the system versus work done by the system in calculations?

3 .

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

### 7.2Electric Potential and Potential Difference

4 .

Discuss how potential difference and electric field strength are related. Give an example.

5 .

What is the strength of the electric field in a region where the electric potential is constant?

6 .

If a proton is released from rest in an electric field, will it move in the direction of increasing or decreasing potential? Also answer this question for an electron and a neutron. Explain why.

7 .

Voltage is the common word for potential difference. Which term is more descriptive, voltage or potential difference?

8 .

If the voltage between two points is zero, can a test charge be moved between them with zero net work being done? Can this necessarily be done without exerting a force? Explain.

9 .

What is the relationship between voltage and energy? More precisely, what is the relationship between potential difference and electric potential energy?

10 .

Voltages are always measured between two points. Why?

11 .

How are units of volts and electron-volts related? How do they differ?

12 .

Can a particle move in a direction of increasing electric potential, yet have its electric potential energy decrease? Explain

### 7.3Calculations of Electric Potential

13 .

Compare the electric dipole moments of charges $±Q±Q$ separated by a distance d and charges $±Q/2±Q/2$ separated by a distance d/2.

14 .

Would Gauss’s law be helpful for determining the electric field of a dipole? Why?

15 .

In what region of space is the potential due to a uniformly charged sphere the same as that of a point charge? In what region does it differ from that of a point charge?

16 .

Can the potential of a nonuniformly charged sphere be the same as that of a point charge? Explain.

### 7.4Determining Field from Potential

17 .

If the electric field is zero throughout a region, must the electric potential also be zero in that region?

18 .

Explain why knowledge of $E→(x,y,z)E→(x,y,z)$ is not sufficient to determine V(x,y,z). What about the other way around?

### 7.5Equipotential Surfaces and Conductors

19 .

If two points are at the same potential, are there any electric field lines connecting them?

20 .

Suppose you have a map of equipotential surfaces spaced 1.0 V apart. What do the distances between the surfaces in a particular region tell you about the strength of the $E→E→$ in that region?

21 .

Is the electric potential necessarily constant over the surface of a conductor?

22 .

Under electrostatic conditions, the excess charge on a conductor resides on its surface. Does this mean that all of the conduction electrons in a conductor are on the surface?

23 .

Can a positively charged conductor be at a negative potential? Explain.

24 .

Can equipotential surfaces intersect?

### 7.6Applications of Electrostatics

25 .

Why are the metal support rods for satellite network dishes generally grounded?

26 .

(a) Why are fish reasonably safe in an electrical storm? (b) Why are swimmers nonetheless ordered to get out of the water in the same circumstance?

27 .

What are the similarities and differences between the processes in a photocopier and an electrostatic precipitator?

28 .

About what magnitude of potential is used to charge the drum of a photocopy machine? A web search for “xerography” may be of use.

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