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Flashcards in Topic 8 Deck (71):
1

The efficiency of a modern natural gas power station is approximately A. 10%.

B. 50%.

C. 75%.

D. 90%

B. 50 %

2

The energy source that currently provides the greatest proportion of the world’s total energy demand is

A. coal.

B. oil.

C. natural gas.

D. uranium.

B. oil. 

3

In a nuclear power station, uranium is used as the energy source and plutonium-239 is produced. Which of the following is true?

A. Plutonium-239 is produced by nuclear fusion.

B. A moderator is used to absorb plutonium-239.

C. Control rods are used to slow down plutonium-239.

D. Plutonium-239 can be used as a fuel in another type of nuclear reactor.

D. Plutonium-239 can be used as a fuel in another type of nuclear reactor.

4

One disadvantage of using photovoltaic cells to power a domestic water heater is that

A. solar energy is a renewable source of energy.

B. the power radiated by the Sun varies significantly depending on the weather.

C. a large area of photovoltaic cells would be needed.

D. photovoltaic cells contain CFCs, which contribute to the greenhouse effect

C. a large area of photovoltaic cells would be needed. 

5

Greenhouse gases

A. reflect infrared radiation but absorb ultraviolet radiation.

B. reflect ultraviolet radiation but absorb infrared radiation.

C. transmit infrared radiation but absorb ultraviolet radiation.

D. transmit ultraviolet radiation but absorb infrared radiation

D. transmit ultraviolet radiation but absorb infrared radiation

6

The rate of global warming might be reduced by

A. replacing the use of coal and oil with natural gas.

B. a reduction in the Earth’s albedo.

C. a reduction in carbon fixation.

D. an increase in deforestation.

A. replacing the use of coal and oil with natural gas. 

7

The unit of energy density of a fuel is

A. Jm–2.

B. Jm–3.

C. J kg–1.

D. kgJ –1

C. J kg–1. 

8

Which of the following is the best estimate for the overall efficiency of a typical coal power station?

A. 5%

B. 30%

C. 60%

D. 90%

B. 30%

9

When sunlight is incident on a solar cell an electric current is produced. This is due to

A. a temperature gradient within the cell.

B. very long wavelength infrared radiation.

C. very short ultraviolet radiation.

D. the photoelectric effect.

D. the photoelectric effect.

10

The power per unit length P of an oscillating water column (OWC)is due to the action of a surface wave of amplitude A. Which of the following correctly relates P and A, and correctly identifies the nature of the energy of the water column?

           Relation between P and A                      Nature of energy

A.                  P∝ A                                                      kinetic

B.                 P∝ A                                             kinetic and potential

C.                 P∝ A2                                                     kinetic

D.                 P∝ A2                                          kinetic and potential

D. relation between P and A isP∝ A2  and the nature of energy is      kinetic and potential

11

The average temperature of the surface of the Sun is about 20 times more than the average surface temperature of the Earth. The average power per unit area radiated by the Earth is P. The average power per unit area radiated by the Sun is

A. 20P.

B. 400P.

C. 8000P.

D. 160000P.

D. 160000P.

12

Global warming reduces the ice and snow cover on Earth. Which of the following correctly describes the changes in albedo and rate of energy absorption by Earth?

                          Albedo                         Rate of energy absorption

A.                   increase                                        increase

B.                      decrease                                    increase

C.                    increase                                       decrease

D.                   decrease                                       decrease

B. the albedo decreases and the rate of energy absorption increases

13

Which of the following energy sources results from the solar energy incident on Earth?

A. Nuclear fission

B. Wind energy

C. Nuclear fusion

D. Geothermal energy

B. Wind energy 

14

Which of the following is a renewable and non-renewable energy source?

                         Renewable                                 Non-renewable

A.                       uranium                                            coal

B.                          tidal                                            uranium

C.                         uranium                                         biogas

D.                         natural gas                                    biogas

B. tidal is renewable and uranium is non-renewable

15

A thermal power station is 20% efficient and generates useful electrical power at 1000MW. The fossil fuel used has an energy density of 50MJkg–1. The mass of fuel in kg consumed every second is given by which of the following?

A. 0.01

B. 0.25

C. 4

D. 100

D. 100

16

Which of the following is likely to increase greenhouse gas concentrations in the atmosphere?

A. Using natural gas instead of coal to generate electrical energy

B. Incineration of waste to generate electrical energy

C. Increased use of wind turbines to generate electrical energy

D. Carbon dioxide capture and storage at the power station

B. Incineration of waste to generate electrical energy 

17

Venus and Earth may be regarded as behaving as black bodies. The mean temperature at the surface of Venus is about 600K and at the surface of Earth is about 300K. Which of the following is the best estimate for the ratio

power radiated per unit area on Earth/power radiated per unit area on Venus ?

A. 1/2 .

B. 1/4 .

C. 1/8 .

D. 1/16 .

D. 1/16

18

In a nuclear power station, a moderator is required to

A. control the rate of fission.

B. reduce heat losses to the surroundings.

C. reduce the energy of high energy neutrons.

D. increase the energy of low energy neutrons.

C. reduce the energy of high energy neutrons. 

19

Degraded energy is energy that is

A. stored in the Earth’s atmosphere.

B. available from non-renewable energy sources.

C. converted into work in a cyclical process.

D. no longer available for the performance of useful work.

D. no longer available for the performance of useful work.

20

Which of the following correctly describes both the role of the moderator and of the control rods in a nuclear reactor?

                 Moderator                                         Control rods

A.       slows down the neutrons      maintain a constant rate of fission

B.      cools down the reactor                extract thermal energy

C.      cools down the reactor       maintain a constant rate of fission

D.        slows down the neutrons         extract thermal energy

A. the moderator slows down the neutrons and control rods maintain a constant rate of fission

21

Which of the following correctly shows the energy change in a photovoltaic cell and in a solar heating panel?

           Photovoltaic cell                         Solar heating panel

A.          solar → electrical                       solar → thermal

B.            electrical → thermal                 solar → electrical

C.             solar → electrical                   electrical → thermal

D.         electrical → thermal                     solar → thermal

A. in a photovoltaic cell the solar energy is converted into electrical energy and in a solar heating panel the solar energy is converted into thermal energy

22

The albedo for the oceans is lower than that for glaciers. This is because, compared to ice, sea water

A. has a greater density.

B. has a greater specific heat capacity.

C. has a greater coefficient of volume expansion.

D. absorbs a greater amount of radiative power

D. absorbs a greater amount of radiative power

23

Which of the following is most likely to reduce the enhanced greenhouse effect?

A. Replace the use of gas powered stations with oil powered stations

B. Replace coal-fired power stations with nuclear power stations

C. Increase the use of all non-renewable energy sources

D. Decrease the efficiency of power production

B. Replace coal-fired power stations with nuclear power stations 

24

Which of the following correctly shows a renewable and a non-renewable source of energy?

           Renewable                              Non-renewable

A.             oil                                          geothermal

B.           wind                                          biofuels

C.           ocean waves                            nuclear

D.           natural gas                                  coal

C. ocean waves are renewable and nuclear is nonrenewable

25

Critical mass refers to the amount of fissile material that

A. will allow fission to be sustained.

B. is equivalent to 235 g of uranium.

C. will produce a growing chain reaction.

D. is the minimum mass necessary for fission to take place.

A. will allow fission to be sustained. 

26

The annual variations of solar power incident per unit area at a particular point on the Earth’s surface is mainly due to the change in the

A. distance between the Earth and the Sun.

B. angle at which the solar rays hit the surface of the Earth.

C. average albedo of the Earth.

D. average cloud cover of the Earth. 

B. angle at which the solar rays hit the surface of the Earth. 

27

The water in a reservoir behind a dam drops from an initial height H0 above a turbine to produce hydroelectricity. At time t =T, h =0.

 The graph shows the variation with time t of the height h of the water above the turbine.

Which of the following is a measure of the maximum theoretical electric power available?

A. H0 and the slope of the graph

B. T and the slope of the graph

C. T and the area under the graph

D. H0 and the area under the graph

Q image thumb

A. H0 and the slope of the graph 

28

Each square metre of the Sun’s surface emits S joules per second. The radius of the Sun is r, and the Sun is at a mean distance R from the Earth. Which of the following gives the solar power incident per unit area of the top layer of the Earth’s atmosphere? 

A. (r/R)S

B. (r/R)2S

C. (R/r)S

D. (R/r)2S

B. (r/R)2S

29

The diagram shows a simple climate model for Earth. The temperature of the ground is Tg and is assumed to radiate as a black body. The temperature of the atmosphere is Ta and has an emissivity ε.

In the model, the intensity radiated from the ground equals the intensity radiated from the atmosphere towards the ground. What is the ratio Tg/Ta ?

A. ε4

B. ε

C. ε1/4

D. 1

Q image thumb

C. ε1/4

30

A wave generator produces a power per unit length of 4.0kWm–1 for waves of amplitude A and speed v. The efficiency of the generator is constant. The power per unit length obtained from waves of amplitude 2A and speed 2v would be

A. 8.0 kWm–1.

B. 16kWm–1.

C. 32kWm–1.

D. 64kWm–1.

C. 32kWm–1

31

The diagram shows the variation with wavelength of the power per unit wavelength I radiated from an area of 1m2 of two different bodies

Which of the following is a correct comparison of the temperature and of the emissivity of the two bodies?

                     Temperature                                  Emissivity

A.                    same                                               same

B.                    same                                              different

C.                    different                                            same

D.                  different                                           different

D. both the temperature and emissivity are different

32

Which of the following is the most likely explanation for a rise in global sea level?

A. Thermal expansion of water

B. Melting of sea ice

C. Increase in rainfall

D. Thermal expansion of ice

A. Thermal expansion of water 

33

 What is the phenomenon that best explains why greenhouse gases absorb infrared radiation?

A. Resonance

B. Interference

C. Refraction

D. Diffraction

A. Resonance 

34

 In which of the following places will the albedo be greatest?

A. A forest

B. A grassland

C. An ocean

D. A polar ice cap

D. A polar ice cap

35

A wind turbine produces a power P when the wind speed is v. Assuming that the efficiency of the turbine is constant, the best estimate for the power produced when the wind speed becomes 2v is

A. 2P.

B. 4P.

C. 6P.

D. 8P.

D. 8P.

36

A spherical black body has absolute temperature T1. The surroundings are kept at a lower absolute temperature T2. What is the net power per unit area lost by the body?

A. σT14

B. σT24

C. σ(T14-T24

D. σ(T14+T24)

C. σ(T14-T24)

37

The design of a nuclear power station includes an electrical generator. The function of the generator is to convert

A. nuclear energy to kinetic energy.

B. kinetic energy to thermal energy.

C. thermal energy to electrical energy.

D. kinetic energy to electrical energy

D. kinetic energy to electrical energy

38

What is the unit of surface heat capacity?

A. J kg-1 K-1 

B. J K−1 .

C. J m-2 K-1.

D. J m-3 K-1.

C. J m-2 K-1

39

The Sankey diagram of a fossil-fuelled power station is shown below.

Which of the following best identifies the thermal energy removed by water and the useful electrical energy output of the station?

       Thermal energy removed        Useful electrical energy output

A.                     2                                                       1

B.                    2                                                        3

C.                     3                                                       1

D.                     1                                                        2

Q image thumb

A. 2 is the thermal energy removed and 1 is the useful electrical energy output

40

World energy resources include coal, nuclear fuel and geothermal energy. Which of the following lists these resources in order of energy use in the world?

A. nuclear, geothermal, coal

B. nuclear, coal, geothermal

C. coal, geothermal, nuclear

D. coal, nuclear, geothermal

D. coal, nuclear, geothermal

41

Which of the following processes leads to the production of a nucleus of plutonium-239 from a nucleus of uranium-238?

A. Neutron capture by uranium nucleus

B. Radioactive decay of uranium nucleus

C. Electron capture by uranium nucleus

D. Nuclear fission of uranium nucleus

A. Neutron capture by uranium nucleus 

42

Surface X has a temperature TX and emissivity εx. Surface Y has a temperature TY and emissivity εy. The two surfaces emit radiation at the same rate. What is the ratio TX/TY ?

A. (Ey/Ex)1/4

B. (Ex/Ey)1/4

C. (Ey/Ex)4

D. (Ex/Ey)4

A. (Ey/Ex)1/4

43

 Large areas of rainforests are cut down and burned every year. The result of these actions is

A. reduced albedo.

B. reduced carbon fixation.

C. increased evaporation rate.

D. increased mass of atmospheric methane

B. reduced carbon fixation. 

44

What is the SI unit of energy density?

A. Js–1

B. J kg–1

C. Jm–2

D. kgm–3

B. J kg–1 

45

In a nuclear fission reaction neutrons are passed through a moderator. The reason for this is to reduce the

A. number of the neutrons.

B. kinetic energy of the neutrons.

C. the number of collisions between neutrons.

D. potential energy of the neutrons.

B. kinetic energy of the neutrons.

46

Wind of speed v is incident normally on a wind turbine of radius r. The maximum theoretical power output of the turbine is P. For wind of speed 2v incident normally on a similar turbine of radius 1/2r, the maximum theoretical power will be

A. 1/2 P.

B. P.

C. 2P.

D. 4P.

C. 2P. 

47

Which of the following geographical features has the lowest albedo?

A. Polar ice cap

B. Desert

C. Ocean

D. White cliffs

C. Ocean 

48

The power emitted as electromagnetic radiation by the Sun is approximately 4×1026W. The radius of the orbit of Mars around the Sun is approximately 2×1011m. What is the best estimate for the power incident on an area of 1m2 at the radius of Mars’ orbit?

A. 103 W

B. 107 W

C. 1011W

D. 1015W

A. 103 W 

49

Which of the following alternatives would be the most likely to increase the enhanced greenhouse effect?

A. Replacement of oil and coal fired power stations with natural gas fired power stations

B. Forests being cut down without being replanted

C. Greater use of combined heating and power systems

D. Use of motor vehicles powered by a combination of electricity and oil products

B. Forests being cut down without being replanted 

50

The fraction of the world’s energy consumption provided by nuclear energy is

A. less than 0.2%.

B. between 0.2% and 2%.

C. between 2% and 20%.

D. greater than 20%.

C. between 2% and 20%

51

The burning of fossil fuels in power stations produces greenhouse gases. Another potential environmental problem is that

A. the emissions can destroy the ozone layer.

B. the emissions can cause acid rain.

C. the maximum efficiency is very low.

D. the energy density of the fuels is low compared to renewable resources.

B. the emissions can cause acid rain. 

52

In a nuclear power station, in order to increase the chances of a chain reaction

A. kinetic energy is removed from the neutrons.

B. kinetic energy is given to the neutrons.

C. some neutrons are absorbed.

D. extra neutrons are added.

A. kinetic energy is removed from the neutrons. 

53

 The original source of the electrical power produced by a wind generator is

A. the Sun’s radiated energy.

B. the gravitational energy of the Sun and the Moon.

C. nuclear energy stored within atoms in the Earth’s atmosphere.

D. the Earth’s internal energy.

A. the Sun’s radiated energy.

54

Increasing the temperature of a black-body will have the following effect on its emission spectrum.

        Total power radiated              Peak wavelength of radiation

A.               increases                                     decreases

B.           stays the same                                decreases

C.             increases                                    stays the same

D.         stays the same                              stays the same

A. the total power radiated increases and the peak wavelength of radiation decreases

55

 A natural process that could cause an increase in global warming is

A. an increase in the radius of the Earth’s orbit around the Sun.

B. an increase in the absorption of carbon dioxide by sea water.

C. a drop in mean sea-level.

D. deforestation as a result of natural ecosystem changes.

D. deforestation as a result of natural ecosystem changes.

56

What is the unit for the coefficient of volume expansion?

A. m3 K–1

B. m3

C. K

D. K–1

D. K–1

57

Which of the following is correct for nuclear fuel in respect of both its energy density and its long-term sustainability?

            Energy density                             Sustainability

A.             high                                            renewable

B.             low                                             renewable

C.              high                                         non-renewable

D.              low                                         non-renewable

C. the energy density is high, the sustainability is non-renewable

58

Which of the following is the primary function of the moderator in a nuclear power station?

A. To control the rate of fission reactions

B. To absorb neutrons

C. To prevent the power station from becoming unsafe

D. To slow down neutrons

D. To slow down neutrons

59

The blades of a certain wind turbine X have radius r. The maximum theoretical available wind power for a given wind speed is P. Another similar turbine Y has blades of radius 2r. What is the best estimate for the maximum theoretical available wind power from turbine Y?

A. 8P

B. 4P

C. P/4 

D. P/8

B. 4P 

60

Attempts to produce a sustained, controlled and viable nuclear fusion reaction have failed because of the difficulty of maintaining

A. high plasma temperatures.

B. high plasma pressure.

C. the fuel supply injection into the plasma.

D. strong magnetic fields.

A. high plasma temperatures. 

61

The property of the molecules of greenhouse gases which leads to their ability to absorb infrared radiation is their

A. resonant frequency.

B. speed of rotation.

C. total electric charge.

D. diameter.

A. resonant frequency. 

62

Gases in the Earth’s atmosphere believed to be responsible for the greenhouse effect include

A. sulfur dioxide, nitrous oxide, water.

B. methane, carbon monoxide, ozone.

C. carbon dioxide, sulfur trioxide, carbon monoxide.

D. water, methane, nitrous oxide.

D. water, methane, nitrous oxide.

63

Which of the following is the most likely cause of the enhanced greenhouse effect?

A. Increased volcanic activity

B. Deforestation

C. Burning of fossil fuels

D. Solar flare activity

C. Burning of fossil fuels 

64

A small biofuel power station burns ethanol with an overall efficiency of 25%. The energy density of ethanol is 30MJkg–1. The mass of fuel consumed every second is 50kg. Which of the following gives the useful power output in MW?

A. (30x50x25)/100 

B. (30x50x100)/25  

C. (30x25)/(50x100) 

D. (30x100)/(50x25)

A. (30x50x25)/100 

65

An oscillating water column ocean-wave energy converter produces power P from waves of a certain amplitude and wavespeed. Which of the following would be the power produced from waves of twice the amplitude and twice the wavespeed?

A. 2P

B. 4P

C. 8P

D. 16P

C. 8P

66

 Carbon dioxide is a greenhouse gas because

A. it absorbs infrared light radiated by the Sun.

B. it absorbs ultraviolet light radiated by the Earth.

C. its natural frequency molecular oscillation lies in the infrared region.

D. its natural frequency molecular oscillation lies in the ultraviolet region.

C. its natural frequency molecular oscillation lies in the infrared region. 

67

Which of the following is most likely to increase the rate of global warming?

A. Deforestation

B. Increasing the use of nuclear power stations

C. Increasing the use of renewable energy sources

D. Using natural gas instead of coal for electricity generation

A. Deforestation 

68

The use of which energy source enhances the greenhouse effect the most?

A. Wood

B. Coal

C. Wind

D. Tidal

B. Coal 

69

The volume expansion coefficient of water is γ . The average depth of the ocean is h. What is the expected fractional increase ∆h/h in the sea level for a temperature increase of ∆θ?

A. γ θ∆ h

B. γ θ∆

C. γh/∆θ

D. γ/∆θ

B. γ θ∆

70

An oscillating water column (OWC) ocean-wave converter produces a power P. What is the power output of this converter if the amplitude and speed of the waves are both doubled?

A. 2P

B. 4P

C. 8P

D. 16P

C. 8P 

71

A student states that the following factors may lead to global warming

I. decreased albedo of the Earth’s surface

II. increase in volcanic activity

III. deforestation.

Which of the above statements are correct?

A. I and II only

B. II and III only

C. I and III only

D. I, II and III

D. I. decreased albedo of the Earth’s surface 

II. increase in volcanic activity 

III. deforestation.