Suppose that a voltage surge produces 140 V for a moment in a 120 V-line. What will temporarily be the output of a 100 W lightbulb assuming its resistance does not change?

1
Suppose that a voltage surge produces 140 V for a
moment in a 120 V-line. What will temporarily be
the output of a 100 W lightbulb assuming its
resistance does not change?

1. 109 W
2. 118 W
3. 127 W
4. 136 W

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2
A solar panel measures 80 cm x 50 cm. In direct
sunlight, the panel delivers 3.2 A at 15 V. If
the intensity of sunlight is 1000 W/m 2 , what is
the efficiency of the solar panel in converting
solar energy into electrical energy?

1. 24.0
2. 18.0
3. 12.0
4. 6.0

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3
A steam turbine at an electric power plant
delivers 4500 kW of power to an electrical
generator which converts 95 of this mechanical
energy into electrical energy. What is the
current delivered by the generator if it delivers
at 3600 V?

1. 0.66 x 103 A
2. 1.0 x 103 A
3. 1.19 x 103 A
4. 5.9 x 103 A

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4
The heating coil of a hot water heater has a
resistance of 20 ohm and operates at 210 V. How
long a time is required to raise the temperature
of 200 kg of water from 15C to 80 C? (the
specific heat for water 103 cal/kg-C and 1.0
cal 4.186 J)

1. 1.7 hr
2. 3.8 hr
3. 5.1 hr
4. 6.9 hr

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5
The heating coil of a hot water heater has a
resistance of 20 ohm and operates at 210 V. If
electrical energy costs 5.5 cents per kW-hr, what
does it cost to raise the 200 kg water
temperature form 15C to 80C? (the specific heat
of water 103 cal/kgC and 1.0 cal 4.186 J)

1. 48 cents
2. 83 cents
3. 16 cents
4. 80 cents

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6
An electric clothes dryer draws 15 A at 220 V. If
the clothes put into the dryer have a mass of 7
kg when wet and 4 kg dry, how long does it take
to dry the clothes? (Assume all heat energy goes
into vaporizing water, Lvap 2.26 x 106 J/kg.)

1. 55.1 min
2. 34.2 min
3. 20.0 min
4. 15.6 min

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7
By what factor is the resistance of a copper wire
changed when its temperature is increased from
20C to 120C? (the temperature coefficient of
resistivity for copper 3.9 x 10-3 /C)

1. 0.72
2. 1.06
3. 1.39
4. 1.44

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8
If a lamp is measured to have a resistance of 120
ohms when it operates at a power of 100 W, what
is the applied voltage?

1. 110 V
2. 120 V
3. 125 V
4. 220 V

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9
If a lamp has a resistance of 120 ohms when it
operates at a power of 100 W, what current does
the lamp carry?

1. 2.10 A
2. 1.2 A
3. 0.91 A
4. 0.83 A

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10
An electric toaster requires 1100 W at 110 Volts.
What is the resistance of the heating coil?

1. 7.5 W
2. 9.0 W
3. 10.0 W
4. 11.0 W

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11
If a 500 W heater carries a current of 4.0 A, how
much does it cost to operate the heater for 30
min if electrical energy costs 6 cents per kW-hr?

1. 1.5 cents
2. 9.0 cents
3. 18.0 cents
4. 36.0 cents

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12
A metal wire has a resistance of 10.00 ohms at a
temperature of 20C. If the same wire has a
resistance of 10.55 ohms at 90C, what is the
resistance of this same wire when its temperature
is -20C?

1. 0.7 W
2. 9.69 W
3. 10.31 W
4. 13.8 W

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13
If a 500 W heater carries a current of 4.0 A,
what is the voltage across the ends of the
heating element?

1. 2000 V
2. 125 V
3. 250 V
4. 0.008 V

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14
If a 500 W heater carries a current of 4.0 A,
what is the resistance of the heating element?

1. 85.7 W
2. 42.8 W
3. 31.3 W
4. 11.2 W

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15
A metal wire has a resistance of 10.00 ohms at a
temperature of 20C. If the same wire has a
resistance of 10.55 ohms at 90, what is the
temperature coefficient of resistivity of this
metal?

1. 7.8 x 10-4/C
2. 12.7 x 10-4/C
3. 0.78 x 10-4/C
4. 1.27 x 10-4/C

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16
A wire carries a steady current of 0.1 A over a
period of 20 s. What total charge passes through
the wire in this time interval?

1. 200 C
2. 20 C
3. 2.0 C
4. 0.005 C

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17
A 0.20 m long metal wire has a radius of 1 cm and
a resistance of 3.2 x 10-5 ohm. What is the
resistivity of the metal?

1. 1.6 x 10-8 ohm-m
2. 5.0 x 10-8 ohm-m
3. 16.0 x 10-8 ohm-m
4. 160 x 10-8 ohm-m

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18
A nichrome wire has a radius of 0.50 mm and a
resistivity of 1.5 x 10-6 ohm-m. What is the
resistance per unit length of this wire?

1. 0.0015 ohm-m
2. 0.95 ohm-m
3. 1.6 ohm-m
4. 1.9 ohm-m

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19
A nichrome wire has a radius of 0.50 mm and a
resistivity of 1.5 x 10-6 ohm-m. If the wire
carries a current of 0.5 A, what is the potential
difference per unit length along this wire?

1. 0.003 V/m
2. 0.95 V/m
3. 1.6 V/m
4. 1.9 V/m

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20
When an electric current exists within a
conducting wire, which of the following
statements describes the condition of any
accompanying electric field?

1. must be zero
2. must be parallel to current flow
3. must be anti-parallel to current flow
4. must be perpendicular to current flow

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21
A high-voltage transmission line carries 1000 A
at 700 kV for a distance of 100 miles. If the
resistance in the wire is 1 W/mile, what is the
power loss due to resistive losses?

1. 10 kW
2. 100 kW
3. 10 MW
4. 100 MW

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22
A copper cable is to be designed to carry a
current of 300 A with a power loss of only 2
Watts per meter. What is the required radius of
the copper cable? (The resistivity of copper is
1.7 x 10-8 W-m)

1. 0.8 cm
2. 1.6 cm
3. 3.2 cm
4. 4.0 cm

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23
An electric car is designed to run off a bank of
12-V batteries with total energy storage of 2 x
107 J. If the electric motor draws 8000 W, what
is the current delivered to the motor?

1. 666 A
2. 444 A
3. 222 A
4. 111 A

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24
A high-voltage transmission line carries 1000 A
at 700,000 V. What is the maximum power carried
in the line?

1. 700 MW
2. 370 MW
3. 100 MW
4. 70 MW

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25
An electric car is designed to run off a bank of
12-V batteries with total energy storage of 2 x
107 J. If the electric motor draws 8000 W in
moving the car at a steady speed of 20 m/s, how
far will the car go before it is "out of juice"?

1. 25 km
2. 50 km
3. 100 km
4. 150 km

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26
A color television set draws about 2.5 A when
connected to 120 V. What is the cost (with
electrical energy at 6/kWh) of running the color
TV for 8 hours?

1. 1.4
2. 3.0
3. 14.4
4. 30.0

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27
A high voltage transmission line of diameter 2 cm
and length 200 km carries a steady current of
1000 A. If the conductor is copper with a free
charge density of 8 x 1028 electrons/m3 , how
long does it take one electron to travel the full
length of the cable? (q 1.6 x 10-19 C)

1. 8 x 102 s
2. 8 x 104 s
3. 8 x 106 s
4. 8 x 108 s

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28
The resistance of a platinum wire is to be
calibrated for low-temperature work. A platinum
wire with resistance 1 W at 20C is immersed in
liquid nitrogen at 77 K (-196C). If the
temperature response of the platinum wire in
linear, what is the expected resistance of the
platinum wire at -196C?(aplatinum 3.92 x
10-3 /C)

1. 0.153 W
2. 0.232 W
3. 1.768 W
4. 1.847 W

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29
Some superconductors are capable of carrying a
very large quantity of current. If the measured
current is 105 A, how many electrons are moving
through the superconductor per second? (qe 1.6
x 10-19 C)

1. 6.25 x 1023
2. 3.12 x 1022
3. 6.25 x 1021
4. 3.12 x 1020

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30
A platinum wire is utilized to determine the
melting point of indium. The resistance of the
platinum wire is 2 W at 20C and increases to
3.072 W as the indium starts to melt. aplatinum
3.92 x 10-3 /C. What is the melting
temperature of indium?

1. 137C
2. 157C
3. 351C
4. 731C

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31
Which is not a force?

1. Gravity
2. Electrical force
3. Electromotive force
4. Friction

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32
The unit of electric current, the ampere, is
dimensionally equivalent to which of the
following?

1. volt x ohm
2. volt/ohm
3. ohm x meter
4. volt/sec

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33
The unit of electric resistance, the ohm, is
dimensionally equivalent to which of the
following?

1. volt/amp
2. volt x meter
3. amp/sec
4. amp/meter

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34
What happens to the resistance of a
superconductor when its temperature drops below
the critical temperature?

1. equals that of a semiconductor of equal
   dimensions
2. increases by two
3. drops to zero
4. reduces to one-half

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35
The quantity, electromotive force, is
dimensionally equivalent to which of the
following?

1. joule x meter
2. joule x coulomb
3. coulomb/ohm
4. joule/coulomb

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36
The unit for rate of energy transformation, the
watt, in an electric circuit is dimensionally
equivalent to which of the following?

1. volt/sec
2. ampere x ohm
3. volt x ampere
4. volt/ohm

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37
The current in an electron beam in a cathode-ray
tube is measured to be 70 µ A. How many electrons
hit the screen in 5 seconds? (qe 1.6 x 10-19
C)

1. 2.19 x 1011 electrons
2. 8.75 x 1013 electrons
3. 2.19 x 1015 electrons
4. 8.75 x 1018 electrons

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38
If a 6 V battery, with negligible internal
resistance, and a 12 ohm resistor are connected
in series, what is the amount of electrical
energy transformed to heat per coul of charge
that flows through the circuit?

1. 0.50 J
2. 3.0 J
3. 6.0 J
4. 72 J

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39
If a 75 W lightbulb operates at a voltage of 120
V, what is the current in the bulb?

1. 0.63 A
2. 1.6 A
3. 9.0 x 103 A
4. 1.1 x 10-4 A

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40
Tripling the current in a circuit with constant
resistance has the effect of changing the power
by what factor?

1. 0.33
2. 1/9
3. 3.0
4. 9.0

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41
Replacing a wire resistor with another of the
same material and length but with three times the
diameter will have the effect of changing the
resistance by what factor?

1. 0.33
2. 1/9
3. 3.0
4. 9.0

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42
The size of the electric current in an electrical
conductor is a function of which of the following?

1. velocity of charge carriers
2. conductor thickness
3. density of charge carriers
4. all of the choices are valid

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43
A superconducting wire's chief characteristic is
which of the following?

1. an extremely great length
2. a large cross-sectional area
3. an extremely high temperature
4. no resistance

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44
When current is flowing in a superconductor,
which statement is not true?

1. A battery keeps the current going.
2. Electrical charges are moving.
3. The resistance is zero.
4. No power is given off in the form of heat.

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45
Ten coulombs of charge start from the negative
terminal of a battery, flow through the battery
and then leave the positive terminal through a
wire, flow through a resistor and then return to
the starting point on this closed circuit. In
this complete process, the ten coulombs

1. do positive work on the battery.
2. receive heat energy from the resistor.
3. have a net loss of potential energy.
4. have no net change in potential energy.

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46
Which process will double the power given off by
a resistor?

1. Doubling the current while doubling the
   resistance
2. Doubling the current by making the resistance
   half as big
3. Doubling the current by doubling the voltage
4. Doubling the current while making the voltage
   half as big

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47
In a carbon microphone, the change in resistance
in the microphone as the sound wave moves the
diaphragm back and forth is caused by the

1. change in length of the carbon resistance.
2. change in temperature of the carbon resistance.
3. change in voltage across the carbon resistance.
4. change in velocity of the carbon resistance.

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48
Which is a unit of power?

1. Kilowatt-hour
2. Watt per sec
3. Ampere ohm
4. Joule per sec

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49
If a certain resistor obeys Ohm's law, its
resistance will change

1. as the voltage across the resistor changes.
2. as the current through the resistor changes.
3. as the energy given off by the electrons in their
   collisions changes.
4. none of the choices, since resistance is a
   constant for a given resistor.

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50
Consider some material that has been cooled until
it has become a superconductor. If it is cooled
even further its resistance will

1. increase
2. decrease
3. stay constant and non-zero
4. none of the choices

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51
A certain material is in a room at 27C. If the
absolute temperature (K) of the material is
doubled, its resistance also doubles. (Water
freezes at 273K.) What is the value for a, the
temperature coefficient of resistivity?

1. 1/C
2. 2/C
3. 0.0033/C
4. 0.038/C

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52
When you flip a switch to turn on a light, the
delay time before the light turns on is
determined by

1. the number of electron collisions per second in
   the wire.
2. the drift speed of the electrons in the wire.
3. the speed of the electric field moving in the
   wire.
4. none of these, since the light comes on instantly.

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53
A flashlight bulb operating at a voltage of 4.5 V
has a resistance of 8 ohm. How many electrons
pass through the bulb filament per second (qe
1.6 x 10-19 coul)

1. 3.7 x 1016
2. 1.8 x 1021
3. 9.4 x 1017
4. 3.5 x 1018

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54
In a certain material there is a current of 16 A
flowing through a surface to the right, and there
is an equal amount of positive and negative
charge passing through the surface producing the
current. How much negative charge passes through
the surface?

1. 8 C/s toward the right
2. 8 C/s toward the left
3. 16 C/s toward the right
4. 16 C/s toward the left

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55
A lightbulb has a resistance of 240 W when
operating at a voltage of 120 V. What is the
current in the lightbulb?

1. 2.0 A
2. 1.0 A
3. 0.5 A
4. 0.2 A

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56
Number 10 copper wire (radius 1.3 mm) is
commonly used for electrical installations in
homes. What is the voltage drop in 40 meters of
10 copper wire if it carries a current of 10
Amps? (The resistivity of copper is 1.7 x 10-8
W-m.)

1. 1.28 volts
2. 0.77 volts
3. 0.50 volts
4. 0.13 volts

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57
If a metallic wire of cross-sectional area 3.0 x
10-6 m2 carries a current of 6 A and has a
mobile charge density of 4.24 x 1028 carriers/m3
what is the average drift velocity of the mobile
charge carriers? (charge value 1.6 x 10 -19
coul)

1. 3.4 x 103 m/s
2. 1.7 x 103 m/s
3. 1.5 x 10-4 m/s
4. 2.9 x 10-4 m/s

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58
What is the resistivity of a metallic conductor,
30 m long, with a uniform cross-sectional area of
3.0 x 10-6 m2 and a resistance of 180 ohm?

1. 0.056 x 106 ohm-m
2. 18 x 10-6 ohm-m
3. 162 x 10-4 ohm-m
4. 18 x 108 ohm-m

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59
What is the potential difference across a 5 ohm
resistor which carries a current of 5 A?

1. 100 V
2. 25 V
3. 4 V
4. 1 V

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60
A 20 ohm platinum wire at 20C with a temperature
coefficient of resistivity of 3.9 x 10-3 /C
will have what resistance at 100C?

1. 14 W
2. 20 W
3. 26 W
4. 28 W

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