Download DC Circuits MC

Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
If a quantity you calculated has units of A s, what is that quantity?
A) charge
B) resistance
C) potential
D) capacitance
E) resistivity
1)
2)
When there is electric current through a metal wire, the moving charges are
A) only protons.
B) only electrons.
C) positive metal ions.
D) negative metal ions.
E) both protons and electrons.
2)
3) When there is electric current through an ionic liquid such as salty water, the moving
3)
charges are
A) only protons.
B) only electrons.
C) only positive ions.
D) only negative ions.
E) both positive and negative ions.
4)
If a quantity you calculated has units of
A) resistance
B) charge
C) resistivity
D) capacitance
E) potential
5) If a quantity you calculated has units of
m what is that quantity?
4)
kg m2
, what is that quantity?
s2 C
5)
A)
capacitance
B) charge
C) resistivity
D) resistance
E) potential
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6) The figure shows electrons passing through a resistor. The arrow shows the direction in
6)
which the electrons are moving. Which of the following statements are correct? (There
could be more than one correct choice.)
A)
The speed of the electrons at point b is the same as it is at point a.
B) The electric potential is lower at point b than at point a.
C) The electrons are moving slower at point b than at point a.
D) The system electrons-metal is losing electric potential energy as the electrons
move through the resistor from a to b.
E) The electric potential is higher at point b than at point a.
7) The figure shows conventional current through a resistor. The arrow shows the
direction of this conventional current. Which of the following statements are correct?
(There could be more than one correct choice.)
A)
The electric potential at point b is the same as it is at point a.
electric potential is higher at point b than at point a.
C) The current at point b is the same as the current at point a.
D) The charges are moving slower at point b than at point a.
E) The electric potential is lower at point b than at point a.
B) The
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7)
8) For the graph shown in the figure, what physical quantity does the slope of the graph
8)
represent for ohmic material?
A)
resistivity
B) power
C)
1/(resistance)
D) 1/(resistivity)
E) resistance
9) For the graph shown in the figure, what physical quantity does the slope of the graph
represent for ohmic material?
A)
resistivity
B) power
C) 1/(resistivity)
D) resistance
E) 1/(resistance)
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9)
10) For the graph shown in the figure, what physical quantity does the slope of the graph
10)
represent for ohmic material?
A)
current
B) power
C) 1/(current)
D) resistivity
E) 1/(resistivity)
11) For the graph shown in the figure, what physical quantity does the slope of the graph
represent for ohmic material?
A)
power
B) resistivity
C) 1/(current)
D) current
E) 1/(resistivity)
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11)
12) You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads
12)
to it in order to make a resistor. If you want to achieve the smallest possible resistance,
you should attach the leads to the opposite faces that measure
A) 3 cm × 8 cm.
B) 3 cm × 5 cm.
C) 5 cm × 8 cm.
D) Any pair of faces produces the same resistance.
13) You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads
13)
to it in order to make a resistor. If you want to achieve the largest possible resistance,
you should attach the leads to the opposite faces that measure
A) 3 cm × 8 cm.
B) 3 cm × 5 cm.
C) 5 cm × 8 cm.
D) Any pair of faces produces the same resistance.
14) Copper wire #1 has a length L and a radius b. Copper wire #2 has a length 2L and a
14)
radius 2b. Which statement about the resistance across the ends of the wires is true?
A) The resistance of wire #1 is four times higher than that of wire #2.
B) The resistance of wire #1 is twice as high as that of wire #2.
C) The resistance of wire #1 is half that of wire #2.
D) The resistance of wire #1 is equal to that of wire #2.
15) The figure shows a graph of the resistance of a wire as a function of its length. What
physical quantities does the slope of this graph represent?
A)
the resistivity of the material divided by the cross-sectional area of the wire
B) the product of the resistivity and the cross-sectional area of the wire
C) the resistivity of the material of which the wire is made
D) the reciprocal of the resistivity of the material
E) the cross-sectional area of the wire
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15)
16) A wire of resistivity
16)
17) The length of a certain wire is kept same while its radius is doubled. What is the new
17)
must be replaced in a circuit by a wire of the same material but
four times as long. If, however, the total resistance is to remain as before, the diameter
of the new wire must
A) be the same as the original diameter.
B) be two times the original diameter.
C) be one-half the original diameter.
D) be four times the original diameter.
E) be one-fourth the original diameter.
resistance of this wire?
A) It is reduced by a factor of 2.
B) It is increased by a factor of 4.
C) It is reduced by a factor of 4.
D) It is increased by a factor of 2.
E) It is reduced by a factor of 8.
18) The length of a certain wire is kept same while its radius is doubled. What is the new
18)
resistivity of this wire?
A) It does not change.
B) It is reduced by a factor of 2.
C) It is reduced by a factor of 4.
D) It is increased by a factor of 2.
E) It is increased by a factor of 4.
19) The length of a certain wire is doubled while its radius is kept constant. What is the
19)
new resistance of this wire?
A) It stays the same.
B) It is 4 times as large.
C) It is 1/2 as large.
D) It is 2 times as large.
E) It is 3 times as large.
20) The length of a certain wire is doubled and at the same time its radius is also doubled.
What is the new resistance of this wire?
A) It is 4 times as large.
B) It is 1/4 as large.
C) It is 2 times as large.
D) It stays the same.
E) It is1/2 as large.
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20)
21) The length of a certain wire is doubled and at the same time its radius is reduced by a
21)
factor of 2. What is the new resistance of this wire?
A) It is 8 times as large.
B) It is 4 times as large.
C) It is 1/2 as large.
D) It is 6 times as large.
E) It is 2 times as large.
22) If a quantity you calculated has units of
kg m2
what is that quantity?
s C2
22)
kg m3
what is that quantity?
s C2
23)
A)
capacitance
B) resistance
C) potential
D) current
E) resistivity
23) If a quantity you calculated has units of
A)
resistance
B) resistivity
C) current
D) potential
E) capacitance
24) Which
one of the following quantities is equivalent to 1 ?
A) 1 W/A
B) 1 V/A
C) 1 A s
D) 1 J/s
24)
E) 1
V A
25) If the length and diameter of a wire of circular cross section are both tripled, the
25)
resistance will be
A) 1/3 of what it originally was.
B) increased by a factor of 9.
C) tripled.
D) unchanged.
E) 1/9 of what it originally was.
26) Consider two copper wires of equal cross-sectional area. One wire has 3 times the
length of the other. How do the resistivities of these two wires compare?
A) The longer wire has 27 times the resistivity of the shorter wire.
B) The longer wire has 3 times the resistivity of the shorter wire.
C) The longer wire has 9 times the resistivity of the shorter wire.
D) Both wires have the same resistivity.
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26)
27) Consider two copper wires of equal cross-sectional area. One wire has 3 times the
27)
length of the other. How do the resistances of these two wires compare?
A) Both wires have the same resistance.
B) The longer wire has 1/3 the resistance of the shorter wire.
C) The longer wire has 9 times the resistance of the shorter wire.
D) The longer wire has 27 times the resistance of the shorter wire.
E) The longer wire has 3 times the resistance of the shorter wire.
28) Consider two copper wires of equal length. One wire has twice the cross-sectional area
28)
of the other. How do the resistances of these two wires compare?
A) The thicker wire has four times the resistance of the thinner wire.
B) The thicker wire has twice the resistance of the thinner wire.
C) The thicker wire has one-fourth the resistance of the thinner wire.
D) The thicker wire has eight times the resistance of the thinner wire.
E) The thicker wire has one-half the resistance of the thinner wire.
29) Consider two copper wires with circular cross-sections and equal lengths. One wire has
29)
3 times the diameter of the other. How do the resistances of these two wires compare?
A) The thicker wire has 1/9 the resistance of the thinner wire.
B) The thicker wire has 9 times the resistance of the thinner wire.
C) The thicker wire has 3 times the resistance of the thinner wire.
D) The thicker wire has 1/3 the resistance of the thinner wire.
E) The thicker wire has 3 times the resistance of the thinner wire.
30) When the current through a resistor is increased by a factor of 4, the power dissipated
30)
by the resistor
A) decreases by a factor of 16.
B) increases by a factor of 2.
C) decreases by a factor of 4.
D) increases by a factor of 4.
E) increases by a factor of 16.
31) Which
one of the following quantities is equivalent to 1 W?
m
A) 1 V/A
B) 1 V A
C) 1
D) 1 V/
32) A
31)
E) 1
A s
32)
kilowatt-hour is equivalent to
A) 3600 J.
B) 3,600,000 J/s.
C) 3600 J/s
D) 1000 W.
E) 3,600,000 J.
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33) If the resistance in a constant voltage circuit is doubled, the power dissipated by that
33)
circuit will
A) increase by a factor of two.
B) decrease to one-fourth its original value.
C) decrease to one-half its original value.
D) increase by a factor of four.
34) If the voltage across a circuit of constant resistance is doubled, the power dissipated by
34)
that circuit will
A) be two times as large.
B) be four times as large.
C) decrease to one-fourth the original power.
D) decrease to one-half the original power.
35) If we double the resistance in a circuit but keep the current through it constant, the
power dissipated by that circuit will
A) be four times as great.
C) be two times as great.
35)
B) be
one-half as great.
D) be one-fourth as great.
36) If the current through a circuit of constant resistance is doubled, the power dissipated
36)
by that circuit will
A) decrease to one-fourth of what it was.
B) decrease to one-half of what it was.
C) quadruple in magnitude.
D) double in magnitude.
37) During a period of high power demand, the voltage output of the power company is
reduced by 5.0%. By what percentage is the power in a resistor decreased?
A) 10%
B) 2.5%
C) 90%
D) 5.0%
E) 15%
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37)
38) The figure shows a graph of the power dissipated in a resistor as a function of the
38)
resistance. What quantity does the slope of this graph represent?
A)
the reciprocal of the current in the resistor
B) the current in the resistor
C) the resistivity of the resistor
D) the potential difference across the resistor
E) the square of the current in the resistor
39) For the graph shown in the figure, what physical quantity does the slope of the graph
represent for a dc circuit?
A)
current
B) energy
C) resistivity
D) capacitance
E) resistance
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39)
40) For the graph shown in the figure, what physical quantity does the slope of the graph
40)
represent for a dc circuit?
A)
1/(resistance)
B) (potential)2
C) resistance
D) 1/(potential)
E) potential
41) Four unequal resistors are connected in series with each other. Which one of the
41)
following statements is correct about this combination?
A) The equivalent resistance is equal to that of any one of the resistors.
B) The equivalent resistance is more than the largest resistance.
C) The equivalent resistance is equal to the average of the four resistances.
D) The equivalent resistance is less than that of the smallest resistor.
E) The equivalent resistance is less than that of the largest resistor.
42) Four unequal resistors are connected in a parallel with each other. Which one of the
42)
following statements is correct about this combination?
A) The equivalent resistance is equal to the average of the four resistances.
B) The equivalent resistance is more than the largest resistance.
C) The equivalent resistance is less than that of the smallest resistor.
D) The equivalent resistance is midway between the largest and smallest resistance.
E) None of the other choices is correct.
43) You buy a AA battery in the store, and it is marked 1.5 V. If this marking is strictly
accurate, while this battery is fresh
A) its terminal voltage will be 1.5 V when it is used in a circuit.
B) its terminal voltage will be more than 1.5 V when it is used in a circuit.
C) its terminal voltage will be less than 1.5 V when it is used in a circuit.
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43)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
44) Draw a circuit with two batteries, a resistor between them, and a capacitor in
parallel with the resistor. The batteries are connected negative pole to positive
pole.
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44)
45) Draw a circuit consisting of a battery connected to two resistors, R 1 and R2, in
45)
series with each other and a capacitor C connected across the resistors.
46) Draw a circuit with a battery connected to four resistors, R1, R 2, R3, and R4, as
follows. Resistors R 1 and R2 are connected in parallel with each other, resistors
R3 and R4 are connected in parallel with each other, and both parallel sets of
resistors are connected in series with each other across the battery.
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46)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
47) When
unequal resistors are connected in parallel in a circuit,
A) the potential drop is always the same across each resistor.
B) the largest resistance has the largest current through it.
C) the power generated in each resistor is the same.
D) there is always the same current through each resistor.
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47)
48) When
48)
49) You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in
49)
unequal resistors are connected in series across an ideal battery,
A) the potential difference across each is the same.
B) the same power is dissipated in each one.
C) the equivalent resistance of the circuit is less than that of the smallest resistor.
D) the equivalent resistance of the circuit is equal to the average of all the resistances.
E) the current through each is the same.
the normal way, you devise a circuit that places them in series across normal household
voltage. If each one is an incandescent bulb of fixed resistance, which statement about
these bulbs is correct?
A) Both bulbs glow with the same brightness, but less than their normal brightness.
B) The 50-W bulb glows more brightly than the 100-W bulb.
C) Both bulbs glow with the same brightness, but more than their normal brightness.
D) The 100-W bulb glows brighter than the 50-W bulb.
50) As more resistors are added in series to a constant voltage source, the power supplied
50)
by the source
A) decreases.
B) increases for a time and then starts to decrease.
C) increases.
D) does not change.
51) As more resistors are added in parallel across a constant voltage source, the power
51)
supplied by the source
A) increases for a time and then starts to decrease.
B) decreases.
C) does not change.
D) increases.
52) When different resistors are connected in parallel across an ideal battery, we can be
certain that
A) their equivalent resistance is greater than the resistance of any one of the
individual resistances.
B) their equivalent resistance is equal to the average of the individual resistances.
C) there is the same current through each one.
D) the power dissipated in each is the same.
E) the potential difference across each is the same.
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52)
53) The lamps in a string of decorative lights are connected in parallel across a
53)
constant-voltage power source. What happens if one lamp burns out? (Assume
negligible resistance in the wires leading to the lamps.)
A) The other lamps get brighter equally.
B) The other lamps get brighter, but some get brighter than others.
C) The other lamps get dimmer equally.
D) The other lamps get dimmer, but some get dimmer than others.
E) The brightness of the lamps will not change appreciably.
54) A 9-V battery is hooked up to two resistors in series using wires of negligible
resistance. One has a resistance of 5 , and the other has a resistance of 10 . Several
locations along the circuit are marked with letters, as shown in the figure. Which
statements about this circuit are true? (There could be more than one correct choice.)
A) The current at A is greater than the current at B, which is equal to the current at C,
which is greater than the current at D.
B) The potential at B is equal to the potential at C.
C) The current is exactly the same at points A, B, C, and D.
D) The potential at D is equal to the potential at C.
E) The current at A is greater than the current at B, which is greater than the current
at C, which is greater than the current at D.
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54)
55) A 9-V battery is hooked up to two resistors in series. One has a resistance of 5
, and
the other has a resistance of 10 . Several locations along the circuit are marked with
letters, as shown in the figure. Which resistor is converting electric energy into internal
energy at the higher rate?
A)
55)
the 10-
resistor
is being dissipated by both resistors at the same rate.
C) the 5- resistor
B) Energy
56) Identical light bulbs can be attached to identical ideal batteries in three different ways
(A, B, or C), as shown in the figure. The ranking (from lowest to highest) of the total
power produced by the battery is
A)
B, A, C
B) A,
C, B
C)
C, A, B
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D)
A, B, C
E) C,
B, A
56)
57) Identical ideal batteries are connected in different arrangements to the same light bulb,
57)
as shown in the figure. For which arrangement will the bulb shine the brightest?
A)
A
B) B
C)
C
58) A resistor is made out of a wire having a length L. When the ends of the wire are
attached across the terminals of an ideal battery having a constant voltage V 0 across its
terminals, there is current I through the wire. If the wire were cut in half, making two
wires of length L/2, and both wires were attached across the terminals of the battery
(the right ends of both wires attached to one terminal, and the left ends attached to the
other terminal), how much current would the battery put out?
A) 2I
B) I/2
C) 4I
D) I
E) I/4
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58)
59) In the circuit shown in the figure, the resistor R has a variable resistance. As R is
59)
decreased, what happens to the currents?
A) I1 increases and I2 increases.
B) I1 decreases and I2 decreases.
C) I1 remains unchanged and I2 increases.
D) I1 increases and I2 decreases.
E) I1 decreases and I2 increases.
60) Kirchhoff's
60)
61) Kirchhoff's
61)
junction rule is a statement of
the
law
of conservation of energy.
A)
B) Newton's second law.
C) the law of conservation of charge.
D) the law of conservation of angular momentum.
E) the law of conservation of momentum.
loop rule is a statement of
A) the law of conservation of charge.
B) the law of conservation of energy.
C) the law of conservation of momentum.
D) the law of conservation of angular momentum.
E) Newton's second law.
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SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
62) For the circuit shown in the figure, write the Kirchhoff current equation for the
62)
node labeled A. Notice the directions of the currents!
63) For the circuit shown in the figure, write the Kirchhoff loop equation for the
entire outside loop. Notice the directions of the currents!
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63)
Answer Key
Testname: UNTITLED2
1) A
2) B
3) E
4) E
5) E
6) A, D, E
7) C, E
8) E
9) E
10) A
11) C
12) C
13) B
14) B
15) A
16) B
17) C
18) A
19) D
20) E
21) A
22) B
23) B
24) B
25) A
26) D
27) E
28) E
29) A
30) E
31) B
32) E
33) C
34) B
35) C
36) C
37) A
38) E
39) A
40) E
41) B
42) C
43) C
44) A
45) A
46) A
47) A
48) E
49) B
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Answer Key
Testname: UNTITLED2
50) A
51) D
52) E
53) E
54) B, C
55) A
56) A
57) C
58) C
59) E
60) C
61) B
62) I1 - I2 + I3 = 0
63) V1 + I3R3 - V 3 - I1R 1 = 0
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