Energy random revision (pages 167-177)

Question 1

In what way is energy transferred when work is done by moving charges?

Answer 1

Electricity

Question 2

In what type of system is the net change in total energy always zero?

Answer 2

A closed system

Question 3

In an electric kettle, how is energy transferred from the thermal energy store of the kettle’s heating element to the thermal energy store of the water?

Answer 3

By heating.

Question 4

What energy store is energy transferred away from when an object falls?

Answer 4

Gravitational potential energy store.

Question 5

Give two energy stores that energy may be mechanically transferred to when two objects collide?

Answer 5

Any two from e.g.:

Thermal energy store
Kinetic energy store
Gravitational potential energy store
Elastic potential energy store.

Question 6

The amount of energy in what energy store is equal to ½ x mass x speed²?

Answer 6

Kinetic energy store

Question 7

What energy store is energy transferred to when an object is stretched?

Answer 7

Elastic potential energy store.

Question 8

True or false? The equation ‘elastic potential energy = ½ x spring constant x extension²’ works for all values of extension of a spring. Explain your answer.

Answer 8

False. The equation only works if the spring has not exceeded its limit of proportionality.

Question 9

True or false? All materials will release te same amount of energy if they cool by the same amount. Explain your answer

Answer 9

False. The amount of energy a material releases depends on the specific heat capacity of that material and the mass of material that is cooling.

Question 10

How does the specific heat capacity of a substance relate to the energy required to increase its temperature?

Answer 10

The higher the specific heat capacity of the substance, the more energy required to increase its temperature.

Question 11

According to the conservation of energy principle, what three things can happen to energy?

Answer 11

It can be transferred usefully, stored, or dissipated.

Question 12

What does it mean when energy is decribed as ‘wasted’ during an energy transfer?

Answer 12

That some of the energy has been transferred to energy stores that aren’t useful.

Question 13

What unit is equal to 1 joule per second?

Answer 13

The watt (W)

Question 14

State the variables represented by each of the letters in the equation

    W P =  \_\_\_\_
      t

Answer 14

P is power
W is work done
t is time

Question 15

How can lubication reduce the amount of wasted energy when two objects are rubbed against each other?

Answer 15

It can reduce the friction between the two objects (this friction is what causes energy to be wasted).

Question 16

What is the name of the process where vibrating particles transfer energy to neighbouring particles?

Answer 16

Conduction.

Question 17

What is meant by ‘convection’?

Answer 17

Convection is where energetic particles move away from hotter regions to cooler regions (and so transfer energy).

Question 18

How does the thermal conductivity of a material affect the rate at which energy is transferred across it by conduction?

Answer 18

The higher the thermal conductivity, the higher the rate of energy transfer.

Question 19

How will increasing the thickness of a building’s walls affect its rate of cooling?

Answer 19

It will reduce its rate of cooling

Question 20

What property is equal to useful power output divided by total power input?

Answer 20

Efficiency

Question 21

Give the equation for efficiency in terms of energy transfers?

Answer 21

efficiency =

useful output energy transfer ÷ total input energy transfer

Question 22

Why can no energy transfer be 100% efficient?

Answer 22

Because some energy will aways be wasted during an energy transfer.

Question 23

State three things that energy resources are used for?

Answer 23

E.g.

Generating electricity
Transport
Heating

Question 24

What is a ‘non-renewable energy resource’?

Answer 24

An energy resource that will runout one day.

Question 25

Define 'renewable energy resource'

Answer 25

An energy resourse that can be replenished as quickly as it is used up (so it'll never run out).

Question 26

Explain why wind power can be considered to be an unreliable way to generate electricity?

Answer 26

Because the amount of electricity generated depends on the wind - if there is no wind, or if the wind is too strong, electricity won't be generated.

Question 27

What do solar cells need in order to generate electricity?

Answer 27

Sunlight

Question 28

Give two advantages of using geothermal power as an energy resource?

Answer 28

Any two from e.g. It can be used to both generate electricity and heat home directly It's reliable (as the rocks underground remain hot and continously provide energy) It does very little damage to the environment.

Question 29

Explain one way that hydro-electric power can have a negative effect of the environment?

Answer 29

Hydro-electric power usually requires the flooding of a vallet. This flooding can e.g.: destroy animal habitats cause the release of greenhouse gasses due to rotting vegetation (which leads to global warming).

Question 30

True or false? Using wave power to generate electricity has no negative effects on the enviornent. Explain your answer

Answer 30

False. While wave power produces no pollution, the turbines used can disturb the seabed and distrupt the habitats of animals.

Question 31

Is wave power considered a reliable way to generate electricity? Explain your answer

Answer 31

No, because its energy output depends on the water waves, which vary a lot based on factors such as the wind.

Question 32

Give one way that using tidal power to generate electricity can affect the environment?

Answer 32

E.g. the tidal barrages used to generate electricity can change the habitat of wildlife in the area.

Question 33

What are bio-fuels?

Answer 33

Renewable energy resources created from plant products or animal dung.

Question 34

Give one way bio-fuels can negatively affect the environent?

Answer 34

Any one from eg.: Burning bio-fuels produces greenhouse gasses. Clearing space to grow crops to produce bio-fuels can destroy anial habitats.

Question 35

Why are fossil fuels considered to be reliable energy resources?

Answer 35

Because there is enough of them to meet current demand (and enough to quickly respond to changes in demand too).

Question 36

How does the emission of sulfur dioxide from burning coal and oil negatively affect the environment?

Answer 36

The sulfur dioxide produces acid rain, which e.g. damages trees and soil.

Question 37

Give one way that using nuclear power to generate electricity can have a negative effect on the environment?

Answer 37

It produces dangerous nuclear wast that is difficult to dispose of?

Question 38

Briefly explain why electricity use has decreased since around the year 2000?

Answer 38

Because more people are now trying to save energy/be more energy efficient.

Question 39

How have government targets caused an increase in the UK's use of renewable energy resources?

Answer 39

They put pressure on energy companies to build more power plants which use renewable energy resources, so the companies don't lose business and money.

Question 40

Give one way that reliability has restricted the use of renewable energy resources?

Answer 40

E.g. a lot of renewable energy resources are less reliable than fossil fuels, so many countries still need to use fossil fuels to meet their energy demands.