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Flashcards in P1 Energy Deck (32):
1

What is a system?

An object or a group of objects

2

State examples of changes in the way energy is stored in a system: Heating

HEATING -
* by heating it causes energy to be transferred into the thermal energy store

3

What are the names of the energy stores?

Energy stores:
1. Thermal
2. Kinetic
3. Gravitational Potential
4. Elastic Potential
5. Chemical
6. Magnetic
7. Electrostatic
8. Nuclear

- When a system changes, energy is transferred: into or away from a system, between different objects or between different energy stores
- Closed systems are systems where energy can neither enter nor leave, net change of energy is always 0

4

What is the equation for Kinetic Energy?

Ek = 1/2mv^2

5

What is the equation for Gravitational Potential Energy store?

Ep = mgh

6

What is the equation for Elastic Potential Energy Stored?

Ee = 1/2ke^2

7

Define 'specific heat capacity'

Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1oC

8

Define power

Power is the rate of energy transfer, or the rate of doing work
Power is measured in watts
One watt = 1 joule of energy transferred per second

9

What are the two equations for power?

P = E/t
P = W/t

10

Explain how two systems transferring the same amount of energy can differ in power output

(for example) a powerful machine is not one that exerts a stronger force it's one that can transfer the most energy in a shorter space of time

11

What is the conservation of energy principle?

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

12

What is meant by 'wasted energy'?

Energy that has dissipated into a store that is not useful

13

How can wasted energy be reduced by lubrication?

Lubrication reduces frictional forces:
- something moves -> usually at least one frictional force acting against it
- this causes some energy in the system to be dissipated (e.g. air resistance from a falling object can transfer energy from the kinetic store to the thermal energy store)
- lubricants reduce friction between objects surfaces
- usually liquids which help objects to flow

14

Describe an experiment to investigate the effectiveness of different insulators

- Pour boiling water into a sealable container to a safe level and then measure mass of water in the container
- Use thermometer to measure initial temperature of the water
- Seal container and leave for 5 minutes, keep time with a stopwatch
- Remove lid and record final temperature
- Repeat this experiment but wrap the container in a different material once it has been sealed with the same mass of water
- Compare the temperature changes of each material

* Thickness of the insulators/materials could be investigated, how that affects temperature change

15

What are the equations for efficiency?

Efficiency = useful output energy transfer / total input energy transfer

Efficiency = useful power output / total power input

16

Suggest and explain ways to increase the efficiency of an intended energy transfer

Insulation, lubrications, streamlined

17

Define what a renewable and non-renewable resource is

Renewable:
- these will never run out
- most sources cause less damage to the environment
- don't provide a much energy, can be unreliable
- solar, wind, water waves, hydro-electricity, bio-fuel, tides and geothermal

Non-renewable:
- will run out one day
- cause damage to the environment
- provide most of our energy
- coal, oil and natural gas

18

Compare ways that the different energy resources are used in transport

Non-renewable:
- petrol + diesel vehicles use fuel from oil
- coal used in steam trains

Renewable:
- vehicles can run on biofuels or on a mix with petrol or disel

19

Compare ways that the different energy resources are used in heating

Non-renewable:
- natural gas most widely used fuel for heating homes in the UK
- gas is used to heat water, pumped into radiators around the home
- coal commonly burnt in fireplaces
- electric heaters (storage heaters) use electricity from non-renewable resources

Renewable:
- geothermal heat pump uses geothermal energy resources to heat buildings
- solar water heaters use the sun to heat water which is then pumped into radiators in buildings
- burning bio-fuel or using electricity generated from renewable resources can also be used for heating

20

Wind Power

- Each turbine has a generator inside that produces electricity
- No pollution except for manufacturing
- Obtrusive and noisy
- 1500 turbines to replace one coal-fired power station (lots of ground needed)
- When the wind stops or too strong it's impossible to increase supply when there's extra demand
- Produce electricity 70-85% of the time
- Initial costs are high, but no fuel costs and running costs are low
- No permanent damage to environment

21

Solar Cells

- Used in remote places, electric road signs and satellites
- No pollution (apart from manufacturing)
- Can be incredibly reliable, only in the daytime
- Can't increase the power output
- High initial costs, energy is free, low running costs
- Used small scale usually

22

Geothermal

- Only in volcanic areas, hot rocks lying close to the surface
- Source is slow decay of radioactive elements
- Reliable and free
- Aren't many suitable locations
- Cost of building plant is high compared to the amount of energy is produced

23

Hydroelectric

- Requires flooding of a valley by building a dam
- No pollution
- Rainwater is stored and allowed out through turbines producing electricity
- Big environmental impact: rotting vegetation (greenhouse gases) and loss of habitat
- Look unsightly when dried up
- Remote locations remotes impact on humans
- Can provide an immediate response to an increased demand of electricity
- No problem with reliability (except in drought)
- Initial costs are high, no fuel costs, minimal running costs
- Great for small scale remote areas

24

Wave-power

- Need lots of small wave-powered turbines around the coast
- No pollultion
- Disturbs seabed, spoils marine life habitat
- Spoils view and a hazard to boats
- Fairly unrelible
- Initial costs are high, no fuel costs, minimal running costs
- Small islands = useful (never large scale)

25

Tidal Barrages

- Big dams across river estuaries with turbines inside
- Tides produced by gravitational pull of the sun and moon
- No pollution
- Prevents free access by boats, spoils view and alters habitat
- Reliable
- Initial costs are high, no fuel costs, minimal running costs
- Significant amount of energy produced

26

Bio-fuels

- Organic matters burnt to produce electricity
- Debate around if it's carbon neutral, only if plants are grown at the rate it's being burnt
- Fairly reliable
- Cannot meet immediate energy demands -> stored
- Costs are high
- Growing crops specific for bio-fuel not food
- Large areas of forest cleared to grow bio-fuels

27

Explain reliability in non-renewable resources

- There's enough fossil and nuclear fuels to meet current demand
- Power plants can respond quickly to changes in demand
- Slowly running out
- Initial costs are high, running costs aren't that expensive
- Low fuel extraction costs
- Cost effective

28

Explain environmental problems from non-renewable sources

- Adds to the greenhouse effect, global warming
- Sulfur dioxide (acid rain) from burning
- Views are spoilt (open-cast mining)
- Oil spillages cause serious environmental problems
- Nuclear power is clean, toxic waste is hard to dispose
- Nuclear power has a risk of a catastrophe
- Nuclear fuel relatively cheap, running costs are high

29

Discuss the topic of changing energy sources used

- Pressure from other countries and the public, governments introducing targets for using renewable energy resources -> puts pressure on energy providers so they don't lose business and money
- Car companies creating hybrid and electric cars in response, growing popularity
- Building new renewable power plants costs money, energy providers are reluctant -> bills rising or though rising taxes
- Ethical issues: wind farms being built next to communities
- Not as reliable, research into making renewable resources more reliable (may take years)
- Personal changes are expensive: new cars or buying solar panels

30

How can wasted energy be reduced by insulation?

Insulation reduces rate of energy transfer by heating (in homes):
- Thick walls that are made from a material with a low thermal conductivity -> slows the rate of energy transfer -> building will cool more slowly
- Cavity walls, inner and outer wall with air in the middle -> reduces energy transferred by conduction through walls
- Cavity wall insulation, air gap filled with foam -> reduces energy transfer by convection in wall cavity
- Loft insulation (e.g. fibreglass wool is a good insulator) -> reduces energy loss by conduction and helps prevent creation of convection currents
- Double-glass windows -> air gap between windows helps prevent loss through conduction
- Draught excluders around doors and windows -> reduces energy transfer by convection

31

State examples of changes in the way energy is stored in a system: Work Done

WORK DONE (another way of saying energy transferred) -
* initial force exerted by someone throwing a ball upwards does work, energy transfer from chemical store in the body to the kinetic energy store of ball and arm
* when current flows through a circuit, work is done against the resistance
* friction between cars brakes and wheels, wheel kinetic energy store to thermal store of surroundings
* collision between stationary object and car, normal contact force does work, cars kinetic energy transferred into other stores (some transferred away by sound waves)

32

State examples of changes in the way energy is stored in a system: Falling Objects

FALLING OBJECTS -
* ball dropped from a height, accelerated by gravity, gravitational force does work
* as it continues energy from gpe store transferred to kinetic store
* for a falling object when there's no air resistance:
energy lost from gpe = energy gained in kinetic