P1: Energy

Question 1

What are the types of energy store?

Answer 1

-Thermal -Kinetic -Gravitational -Elastic potential -Chemical -Magnetic -Electrostatic -Nuclear

Question 2

What are the types of energy transfer?

Answer 2

-Mechanically (by a force doing work) -Electrically (work done by moving charges) -By heating -By radiation (through the EM spectrum, e.g. light or UV radiation) Overall, energy can be transferred by heating or by doing work.

Question 3

What is a closed system?

Answer 3

Closed systems are ones where neither energy nor matter can leave. The net change in total energy is always zero.

Question 4

What is the equation for kinetic energy?

Answer 4

Kinetic energy (J) = ½ x mass (kg) x velocity2 (m/s) Ek = ½ mv2

Question 5

What is the equation for gravitational potential energy?

Answer 5

Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m) Ep = mgh

Question 6

What is the law of conservation of energy?

Answer 6

Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed.

Question 7

Dissipated energy is often referred to as ___ energy. This is usually transferred to a useless ___ store.

Answer 7

1) wasted 2) thermal energy

Question 8

What is power and what is it measured in?

Answer 8

Power is the rate of energy transfer / work done, measured in watts (W).

Question 9

What are the two equations for power?

Answer 9

1) Power (W) = energy transferred (J) ÷ time (s) P = E/t 2) Power = work done (J) ÷ time (s) P = W/t

Question 10

No device is 100% efficient, except for ____.

Answer 10

electric heaters

Question 11

What are the two ways to calculate efficiency?

Answer 11

1) Efficiency = useful energy output ÷ total energy input 2) Efficiency = useful power output ÷ total power input

Question 12

What causes energy to be wasted?

Answer 12

When something moves, there’s usually at least one frictional force acting against it, causing some energy in the system to be dissipated.

Question 13

What are three ways to reduce unwanted energy transfers?

Answer 13

1) Lubrication 2) Streamlining 3) Thermal insulation

Question 14

How can lubrication reduce unwanted energy transfers?

Answer 14

Lubrication reduces frictional forces between surfaces of objects that are being rubbed together.

Question 15

Why are lubricants usually liquids (e.g. oil)?

Answer 15

So that they coat objects and flow easily.

Question 16

How can streamlining reduce unwanted energy transfers?

Answer 16

Streamlining reduces air resistance. Air resistance transfers energy from an object’s kinetic to thermal energy store.

Question 17

In what two ways can heating occur?

Answer 17

1) Conduction 2) Convection

Question 18

How does heating occur by conduction?

Answer 18

-When an object is heated, energy is transferred to the kinetic energy stores of its particles. -This causes them to vibrate more and therefore collide more with each other. -During these collisions, energy is transferred between the particles’ kinetic energy stores: this is conduction.

Question 19

How does heating occur by convection?

Answer 19

-If particles are free to move (so in a gas/liquid), an increase in temperature means that energy is transferred to the kinetic energy stores of its particles. -Particles move faster, so spacing between particles therefore increases. -This causes the density of a heated region to decrease. -The warmer, less dense region will rise above cooler, denser regions. -So more energetic particles move from hotter to cooler regions: this is convection.

Question 20

What are three examples of thermal insulation? (conduction)

Answer 20

-Having thick walls made from a material with low thermal conductivity. -Cavity walls: an inner and outer wall with an air gap in the middle. The gap reduces the amount of energy transferred by conduction through the walls. -Double glazing works in the same way: the air gap between two sheets of glass prevents energy transfer by conduction through the windows.

Question 21

What are three examples of thermal insulation? (convection)

Answer 21

-Cavity wall insulation is where the gap between walls is filled with foam, which reduces energy transfer by convection in the wall cavity. -Loft insulation can reduce convection currents (a cycle where air particles are constantly heated, so rise, then cool and sink back down) being created in lofts. -Draught excluders around doors and windows reduce energy transfers by convection.

Question 22

What is specific heat capacity?

Answer 22

The amount of energy required to raise the temperature of 1 kg of a substance by 1ºC.

Question 23

The formula for specific heat capacity is given (ΔE = mcΔθ). What is its symbol and unit?

Answer 23

Symbol: c

Unit: J / kg°C

Question 24

Describe how you would find the specific heat capacity of a solid block of a material.

Answer 24

• You’ll need a solid block of the material, with 2 holes for the heater and thermometer to go into.
• Measure the block’s mass using a balance.
• Wrap it in an insulating layer (decreases energy dissipated from block to surroundings).
• Connect a heater to a power supply and ammeter, and place it into one of the object’s holes.
• Place a thermometer into the other and measure the initial temperature of the block.
• Set the power supply at 10V, then turn it on and immediately start a stopwatch.
• The current transfers energy to the heater’s thermal energy store, which is then transferred to the object’s.
• The ammeter reading should remain constant.
• Measure the temperature on the thermometer every 30 seconds. Turn off the power when you have 10 readings.
• Find the energy transferred to the heater at each reading using the formula E = VIt (bc E = Pt and P = VI).
• Assuming all the energy transferred to the heater was transferred to the block, find the SHC using the rearrangement c = ΔE/mΔθ.
• The plotted relationship between energy transferred and temperature would be directly proportional.

Question 25

Describe how you could investigate the effectiveness of different insulators.

Answer 25

• Boil water in a kettle and use a balance to pour a set mass into a beaker.
• Use a thermometer to measure the initial temperature.
• Seal the beaker with a lid and use a stopwatch to leave it for 5 minutes.
• Remove the lid and measure the water’s final temperature.
• Pour away the water; allow the beaker to cool to room temperature.
• Repeat steps 1-4 (use same mass of water each time!), wrapping the beaker in a different material (foil, newspaper, bubble wrap) each time.
• The most effective insulator is that which reduces the temperature difference by the largest degree.

^{<em>This investigation could be modified to instead test how the thickness of an insulator affects heat loss.</em>}

Question 26

What are non-renewable energy resources?

Answer 26

Non-renewable energy resources are ones that cannot be replenished as they are used up. They usually do damage to the environment.

Question 27

Specifically what are non-renewable energy resources?

Answer 27

They are nuclear fuel (uranium and plutonium) and fossil fuels (natural resources that form underground over millions of years, typically burnt to provide energy). The three main ones are coal, oil and natural gas.

Question 28

Non-renewables provide most of our energy. Why?

Answer 28

They are reliable. There is enough fuel to meet current demand, and they are extracted at a fast enough rate that power plants always have fuel in stock, so they can respond quickly to changes in demand.

Question 29

What are the pros of fossil fuels?

Answer 29

• Reliable.
• Enough to meet current demand and respond to changes in demand.
• Cost effective: while the setup costs of power plants are high, running and fuel extraction costs are fairly low.

Question 30

What are the cons of fossil fuels? Give at least three.

Answer 30

• Finite/non-renewable.
• They release CO₂ into the atmosphere when burned, adding to the greenhouse effect and global warming.
• Power plants ruin the view.
• Burning coal and oil releases sulfur dioxide, causing acid rain. Reduced by taking sulfur out before combustion.
• Coal mining, especially open cast, ruins the landscape.
• Oil spillages cause serious environmental problems.

Question 31

What are the pros of nuclear power?

Answer 31

• Reliable.
• Enough to meet current demand.
• Power plants can respond to changes in demand.

Question 32

What are the cons of nuclear power? Give at least three.

Answer 32

• Finite/non-renewable
• Power plants ruin the view.
• Nuclear waste is dangerous and hard to dispose of.
• Fuel is relatively cheap, but overall cost of nuclear power is high due to cost of power plants and final decommissioning.
• Nuclear power carries the risk of a major catastrophe.

Question 33

What are renewable energy resources?

Answer 33

Natural energy sources that will never run out if we replenish them as they’re used. Most of them do damage to the environment, but less than non-renewables do.

Question 34

Why don’t renewables provide the majority of our energy?

Answer 34

• They aren’t very efficient.
• They are unreliable; they depend on the weather.
• They often can’t respond to changes in demand.

Question 35

What are all the types of renewable energy resources?

Answer 35

-Solar -Wind -Water waves -Hydroelectricity -Biofuel -Tides -Geothermal

Question 36

What are the uses of non-renewable energy resources in transport?

Answer 36

-Petrol and diesel powered vehicles use fuel from oil. -Coal is used in old-fashioned steam trains to boil water and produce steam. -Electricity is used to power vehicles and can be generated from non-renewable resources.

Question 37

What are the uses of renewable energy resources in transport?

Answer 37

-Vehicles that purely run on biofuels. -Electricity is used to power vehicles and can be generated from renewable resources.

Question 38

What are the uses of non-renewable energy resources in heating?

Answer 38

-Natural gas is the most widely used fuel for heating homes in the UK. It’s used to heat water which is pumped into radiators, and to cook food. -Coal is commonly burnt in fireplaces. -Electric heaters can use energy generated by non-renewables.

Question 39

What are the uses of renewable energy resources in heating?

Answer 39

-Ground source heat pumps use geothermal energy resources to heat buildings. -Solar water heaters use the sun to heat water, which is then pumped into radiators. -Electric heaters can use energy generated by renewables, or heat generated by burning biofuels.

Question 40

What are the pros of tidal power?

Answer 40

• No pollution.
• Initial costs are moderately high, but no fuel costs and minimal running costs.
• Reliable; tides happen twice a day without fail and always around the predicted height.
• Has the potential for generating a significant amount of energy.

Question 41

What are the cons of tidal power?

Answer 41

• Prevents boat access.
• Spoils the view.
• Alters the habitats of wading birds, sea creatures and beasties that live in the sand.
• When tides are lower (neap tides), significantly less energy is supplied.
• Tidal barrages don’t work when the water level is equal on either side of the barrage- happens 4 times a day.
• Can only be used in some estuaries.

Question 42

What are the pros of solar power?

Answer 42

-Causes no pollution (apart from manufacturing panels). -Aside from the initial costs, energy is free and running them costs very little. -Reliable source of energy, especially in sunny places.

Question 43

What are the cons of solar power?

Answer 43

-Panels require a lot of energy to manufacture. -They only work in the daytime. -Power output cannot be increased when there is extra demand. -They can’t produce as much energy as other non-renewable sources.

Question 44

What are the uses of solar energy?

Answer 44

Tends to be on a small scale: -Charging calculator and watch batteries which don’t require much energy. -Used in remote places where there’s not much choice. -Powering road signs and satellites.

Question 45

What are the pros of wave power?

Answer 45

-No pollution. -Initial costs are high, but no fuel costs and minimal running costs. -Useful way to generate energy on a small scale, on small islands.

Question 46

What are the cons of wave power?

Answer 46

• Disturbs the seabed and habitats of marine animals.
• Spoils the view.
• Hazard to boats.
• Can’t respond to changes in demand.
• Unreliable; waves tend to die out when the wind drops.

Question 47

Where are wave and wind turbines located?

Answer 47

Wave: around the coast. Wind: exposed places, e.g. the coast or on moors.

Question 48

What are the pros of wind power?

Answer 48

-Causes no pollution (apart from manufacturing). -No fuel costs and minimal running costs. -No permanent damage to the landscape.

Question 49

What are the cons of wind power?

Answer 49

• Production costs are quite high.
• They spoil scenery; a lot of them are needed to replace one coal power station.
• They can be very noisy.
• Dependant on the weather.
• Power output cannot be increased with demand.

Question 50

Where and how is geothermal energy sourced?

Answer 50

Geothermal power is harnessed from underground stores of thermal energy. The source of much of the energy is the decay of radioactive elements (e.g. uranium) deep inside the Earth.

Question 51

How is geothermal energy used?

Answer 51

It can be used to generate electricity or heat buildings directly.

Question 52

Where is it possible to harness geothermal energy on a large scale?

Answer 52

In volcanic areas or where hot rocks lie close to the surface.

Question 53

What are the pros of geothermal power?

Answer 53

-Free. -Reliable. -Does little damage to the environment.

Question 54

What are the cons of geothermal power?

Answer 54

-There aren’t very many suitable locations for power plants. -The cost of power plants is high compared to the amount of energy they produce.

Question 55

What reduces the effect of hydroelectric power on humans?

Answer 55

Putting them in remote valleys, although this still affects animals.

Question 56

What are the pros of hydroelectric power?

Answer 56

-No pollution. -Initial costs are high, but no fuel costs and minimal running costs. -It can provide an immediate response to an increased demand for electricity. -Useful way to generate electricity on a small scale in remote areas.

Question 57

What are the cons of hydroelectric power?

Answer 57

-Flooding of valleys destroys habitats, causes the loss of villages, and causes vegetation to rot, releasing methane and CO2. -Reservoirs can look ugly when they dry out. -Unreliable; depends on the weather and is redundant during droughts.

Question 58

What are biofuels?

Answer 58

Fuels taken from [recently] living materials, e.g. plant products and animal waste. -They can be solid, liquid or gas. -They can be burnt to produce electricity, or run cars, in the same way as fossil fuels.

Question 59

What are the pros of biofuels?

Answer 59

-They can be carbon neutral (fuels that take in as much CO2 from the atmosphere as is released when they are burnt). -Fairly reliable; crops don’t take long to grow and different ones can be grown all year round. -Can be stored for when needed to accomodate for increases in demand.

Question 60

What are the cons of biofuels?

Answer 60

• They can’t respond to immediate energy demands (but they can be stored for when needed).
• The cost of refining biofuels is very high.
• Growing crops specifically for biofuels risks leaving a lack of space and water to meet demands for food crops.
• Causes deforestation; many populations have lost their natural habitats as a result.
• The decay and burning of forest vegetation also increases CO2 and methane emissions.

Question 61

Describe the trends in use of energy in the UK over time.

Answer 61

-Over the 20th century, there was a high increase in energy use as people began to use electricity for more things. -Since the beginning of the 21st century, energy use has been slowly decreasing as appliances have been made more efficient and people have been pushed to be more careful with energy use in the home.

Question 62

Why do people want to use renewable energy resources?

Answer 62

-Fossil fuels are damaging to the environment. -People and governments are becoming increasingly eager to get used to using renewables before non-renewables eventually run out.

Question 63

How has the way we use energy changed?

Answer 63

-Pressure from other countries and the public has meant that governments have begun to introduce targets for using renewables. This has put pressure on energy providers to build power plants that use renewables to make sure they don’t lose business. -Car companies have also been affected by the change in attitude towards the environment- electric cars and hybrids are already on the market, with increasing popularity.

Question 64

What factors limit the use of renewables?

Answer 64

Reliability, money and politics.

Question 65

How does reliability limit the use of renewables?

Answer 65

-Renewables are often unreliable or unable to increase their power output on demand. -This means either having to use a combination of power plants (expensive) or researching ways to improve reliability and cost. -Research takes time and money. Until it’s conducted, we have to use dependable non-renewables.

Question 66

How does money limit the use of renewables?

Answer 66

-Research on improving the reliability and cost of renewables takes time and money. -Making personal changes, e.g. hybrid cars and solar panels, can be expensive. Although the cost of these things is decreasing, they are not an option for many. -Building power plants for renewables is expensive. Many energy providers are reluctant to do this, since fossil fuels are so cost effective. The cost of switching to renewables has to be paid either by customers in their bills or taxes. Some don’t want to or can’t afford to pay.

Question 67

How does politics limit the use of renewables?

Answer 67

-The cost of switching to renewables has to be paid by customers in their bills or taxes. Some people don’t want to or can’t afford to pay. There are debates over whether it’s ethical to make them. -There’s a lot of scientific evidence supporting renewables, but scientists can only advise people. They don’t have the power to change the behavior of the public, governments or companies. -There is debate over whether it’s ethical to make people put up with power plants for renewables built next to them if they don’t agree with the reasons for their use.