Chapter 20 - Topics
Pre-Assessment
Multiple Choice.
Choose the one alternative that best completes the statement or answers the question.
Which one of the following situations results in a conventional electric current that flows westward?
A) A beam of protons moves eastward.
A) A beam of protons moves eastward.
B.
B) An electric dipole moves westward.
C.
C) A beam of electrons moves westward.
D.
D) A beam of electrons moves eastward.
E.
E) A beam of neutral atoms moves westward.
T
he potential difference across the ends of a wire is doubled in magnitude.
If Ohm’s law is obeyed, which one of the following statements concerning the resistance of the wire is true?
A.
A) The resistance is one half of its original value.
B.
B) The resistance is twice the original value.
C.
C) The resistance is not changed.
D.
D) The resistance increases by a factor of four.
E.
E) The resistance decreases by a factor of four.
Which one of the following statements concerning resistance is true?
A.
A) The resistance of a semiconductor increases with temperature.
B.
B) Resistance is a property of resistors, but not conductors.
C.
C) The resistance of a metal wire changes with temperature.
D.
D) The resistance is the same for all samples of the same material.
E.
E) The resistance of a wire is inversely proportional to the length of the wire
Which one of the following statements concerning superconductors is false?
A.
A) Below its critical temperature, the resistivity of a superconductor is zero
Ω
-m.
B.
B) Critical temperatures for some superconductors exceed 100 K.
C.
C) All materials are superconducting at temperatures near absolute zero kelvin.
D.
D) A constant current can be maintained in a superconducting ring for several years without an emf.
E.
E) Superconductors are perfect conductors.
Complete the following statement:
The unit kilowatt • hour measures
The unit kilowatt • hour measures
A.
A) current.
B.
B) energy.
C.
C) power.
D.
D) potential drop.
E.
E) voltage.
Which one of the following quantities can be converted to
kilowatt
•
hours
(kWh)?
A.
A) 2.0 A
B.
B) 8.3 V
C.
C) 5.8 J
D.
D) 9.6 W
E.
E) 6.2 C/V