Deck 6: Electricity

Question 1

What quantity is the same for three resistors in a parallel circuit?

A) power
B) resistance
C) voltage across them
D) current

Answer 1

C

Question 2

A 100 ohm and a 150 ohm resistor are connected in parallel to a 120 V source. What is the current through the 150 ohm resistor?

A) 0.5
B) 0.8
C) 1.2
D) 1.8
E) 2.0 amps

Answer 2

B

Question 3

The magnetic field of a bar magnet is similar to that produced by ________.

A) a current carrying wire shaped like a coil
B) a horseshoe magnet
C) a straight current carrying wire

Answer 3

A

Question 4

A bird sitting on a bare high voltage wire is not electrocuted because

A) of the high resistance of its body
B) there is no electrical potential difference across its body
C) its body is at a low electrical potential compared to the wire
D) the high voltage across its feet produced a small current

Question 5

Superconductors have a primary advantage in that they will _______.

A) reduce heating losses in transmission lines
B) provide large magnetic fields for levitation
C) be able to conduct more current
D) allow electric motors to run almost forever

Question 6

What will be the approximate cost of running a 2 watt clock for one week when electricity
Costs 8¢ per kWh?

A) 0.1¢
B) 3¢
C) 11¢
D) 16¢
E) 115¢

Question 7

One of the fundamentals of static electricity is that the force between two charges of like charge

A) is attractive
B) is repulsive
C) is neutralized
D) is zero

Question 8

Electricity is transmitted from power plants at ________.

A) high voltages
B) high currents
C) low resistances
D) low power

Question 9

Pumped storage generally will enable a utility to _______.

A) increase the efficiency of their electrical generating system
B) store energy until the demand is high enough
C) raise electrons to higher energy states
D) increase their electrical potential energy

Question 10

If a 20 and a 40 ohm resistor are wired in parallel to a 20V source, what will be the current in the 40 ohm resistor?

A) 0.33
B) 0.5
C) 1.0
D) 2.0
E) 3.0 amps

Question 11

Revenue from a 10 MWe electrical power plant over 24 hours when electricity is sold at 7¢/kwh will be about:

A) $1,700
B) $17,000
C) $34,000
D) $340,000
E) $700,000

Question 12

The fuel that provides most of the electricity in the U.S. is ________.

A) oil
B) natural gas
C) coal
D) uranium
E) solar

Question 13

If a 20 and a 40 ohm resistor are wired in series to the same source, the current through the 40 ohm resistor will be:

A) 0.33
B) 0.5
C) 1.0
D) 2.0
E) 3.0 amps

Question 14

Static charge can build up quickly on an object ________.

A) during days when the conditions are not humid
B) when the object is in good electrical contact with the ground
C) only when it is in contact with a good conductor
D) only when the object is moving

Question 15

Alternating current has an advantage over direct current because ________.

A) one can step up the voltage that one can use
B) batteries can be displaced in most circuits
C) electrical generators can be made to function
D) incandescent lights will only work with AC

Question 16

Cosmic rays impinging upon the earth will generally ____.

A) be deflected by the earth's gravitational field
B) not be affected if they are electrically neutral
C) be weaker in intensity at the earth's poles
D) lead to lightning discharges in the atmosphere

Question 17

How much current is drawn by a 1500 W appliance operating at 120V?

A) 2
B) 8
C) 12
D) 15
E) 24 amps

Question 18

How much current will be drawn by a 1200 watt hair dryer operating at 120 volts?

A) 0.1
B) 1.0
C) 1.44
D) 10
E) 20 amps

Question 19

The electrical force between two particles of unlike charge will be ________.

A) repulsive
B) attractive
C) zero

Question 20

The largest share of renewable energy in the U.S. comes from

A) wind
B) natural gas
C) hydro
D) petroleum
E) radiant solar

Question 21

The efficiency of a solar cell is the ratio (numerator to denominator) of the ______.

A) heat plus electricity produced to the solar input
B) light output to the electrical energy input
C) electricity output to the heat output
D) electricity output to the solar input
E) heat input to the electricity output

Question 22

EMF's from electrical lines ________.

A) drop off with the distance squared from the line
B) are only an influence for high voltages
C) have been positively shown to cause cancer in children
D) are not important inside houses.

Question 23

If the average wind speed for 24 hours is 15 mph at one site, but 10 mph for 12 hours and then
20 mph for 12 hours at another site, how much output can be expected from the same turbine situated at the first site compared to the second site?

A) three-quarters
B) half
C) one quarter
D) one eighth
E) same, since the average wind speeds are the same

Question 24

What is not a life-cycle cost associated with a power plant?

A) capital cost
B) maintenance
C) cost of electricity sold
D) fuel cost
E) staffing

Question 25

A device which transforms electrical energy into mechanical energy is a _________.

A) magnet
B) transformer
C) generator
D) motor

Question 26

For light bulbs of different wattages connected in a series circuit, the _______ will be the same for each when ON.

A) current
B) voltage
C) power
D) resistance

Question 27

How much money does it cost to leave on 10 60 watt lights for 15 hours, if the cost of electricity is 8 cents per kWh?

A) 15¢
B) 32¢
C) 72¢
D) 120¢
E) 480¢

Question 28

The overall efficiency of a power plant can be increased by "co-generation", that is, by ________.

A) recycling the waste heat from a power plant back to the boiler
B) raising the temperature of the steam by the use of two boilers
C) combining two types of steam engines to generate electricity
D) generating electricity and using some of the waste heat to provide process steam

Question 29

If the current through a 5 ohm and a 10 ohm resistor in series is 4 amps, then the total voltage drop across both of these resistors will be

A) 15
B) 20
C) 60
D) 120 volts

Question 30

For photovoltaic cells, the potential difference for two silicon cells in series will at
Most be ________.

A) 0.1
B) 0.5
C) 1.0
D) 2.0
E) 5.0 volts.

Question 31

One of the possible dangers of EMF's are ________.

A) radio system interference
B) their potential to produce a shock
C) biological effect of small magnetic fields
D) electrocution

Question 32

Co-generation has the advantage that ________.

A) more energy is generated than is put into the system
B) the overall efficiency of the energy conversion process increases
C) more waste heat is generated
D) solar energy can be utilized to a greater extent

Question 33

A transformer can only operate if _________.
A) the power in equals the power out

A)c. is used
B) the potential difference is large enough
C)
D) we step up the voltage

Question 34

The site location for a wind turbine is especially important. If the power output goes as the cube of the wind velocity, then which of the following average velocities will give approximately twice as much output as a 10 mph wind?

A) 13
B) 20
C) 30
D) 60
E) 80 mph