Conservation of Energy

Question 1

What is the principle of energy conservation?

Answer 1

Energy can neither be created or destroyed, only transferred, stored and dissipated
Total energy input = useful energy output + waster energy

Question 2

What are the three categories of energy transfers and what decides the two types of output energies?

Answer 2

Input, output and waste. The empirical experience of the characteristics decides if it is either waste or useful ( if it is required for the purpose).

Question 3

What is the diagram that shows energy transfers and what is important about the width of the arrows?

Answer 3

A Sankey diagram.

Both arrows must equal the width of the total energy imputed.

Question 4

What is the equation for efficacy?

Answer 4

Efficacy = useful output energy divided by total input energy x 100 %

Question 5

What does it mean if a filament light bulb is less efficient than an energy saving lightbulb?

Answer 5

It means that the total percentage of useful energy in a filament lightbulb is smaller than in an energy efficient one.

Question 6

What is the equation of kinetic energy?

Answer 6

Kinetic energy = 1/2 x mass x velocity squared

Mass(kg) velocity (m/s)

Question 7

What is the equation for gravitational potential energy?

Answer 7

Gravitational potential energy = gravitational field strength x mass x height ( GPE = G x M x H )
Or
Gravitational potential energy = weight x height ( GPE = W x H)

Question 8

What are the energy resources( ways if generating energy )?

Answer 8

Hydro electrical, geothermal, fossil fuels, wind, solar, waves, biomass, nuclear, tidal.

Question 9

What are the advantages and disadvantages renewable energy resources?

Answer 9

Renewable disadvantages: 
unreliable 
Expensive for original purchase
Place dependent 
Engineers have to take into consideration bird migration routes.
Renewable advantages : 
Relatively cheap to run once bought 
Eco- friendly 
Can be reliable e.g. tidal

Question 10

What are the disadvantage and advantages of non- renewable energy resources?

Answer 10

Non-renewable Advantages :
Affordable 
Cheap 
Easy to transport 
Reliable 
Non-renewable disadvantages:
Bad for the environment 
Slowly running out - Consumption is quicker then manufacture 
Dangerous to dispose of

Question 11

How has the use of energy differed over time and why?

Answer 11

The use if energy has differed over time as we are slowly beginning to run out of fossil fuels due to the high levels of consumption over the past years. We are experiencing the drawbacks of non-renewable energy now such as climate change and global warming so the desire to convert to renewable energy is beginning.

Question 12

What is kinetic and thermal energy?

Answer 12

Kinetic - anything moving has energy in its kinetic energy store (mass and speed determines how much)e.g. the great the mass the more energy so faster it travels
Thermal(heat) - any object (the hotter it is the more energy it has)

Question 12

What is chemical and gravitational potential energy?

Answer 12

Chemical -anything that can release energy by a chemical reaction
Gravitational potential - anything in a gravitational field strength (anything that can fall)

Question 12

What is elastic potential and electrostatic energy?

Answer 12

Elastic potential - anything stretched such as springs or bands
electrostatic - to charges that attract or repel each other

Question 13

What are magnetic and nuclear energy stores?

Answer 13

Magnetic - two magnets that attract or repel each other

Nuclear - atomic nuclei release energy from this store in nuclear radiation

Question 14

What is the equation for kinetic energy?

Answer 14

Kinetic energy = 0.5 x mass x velocity2

Question 15

What is the equation for gravitational potential energy?

Answer 15

Change in GPE = mass x gravitational field strength x change in vertical height

Question 16

How can energy be mechanically transferred?

Answer 16

-Mechanically - a force acting on an object like push

Question 17

When is energy useful?

Answer 17

When it is transferred from one store to a useful store

Some energy is usually dissipated as heat to the surroundings

Question 18

What is lubrication?

Answer 18

Lubrication reduces energy transferred by friction (usually when something is moving

Question 19

How does lubrication work?

Answer 19

It reduced friction by lubricating object surfaces with liquids such as oil so they can flow easier.
This reduced heat loss but also reduces wear and tear so is often used in machines

Question 20

What is insulation?

Answer 20

Reduced the rate of energy transfer by heating

Question 21

How does insulation work?

Answer 21

• In a building, the lower the thermal conductivity of its walls the slowed the rate if energy transfer through them (cool slower) so insulates buildings (or you can make walls thicker)
• Cavity walls with an air gap between inner and outer walls reduces energy transferred by conduction as air has low thermal conductivity

Question 22

What is biofuel, the advantages and disadvantages?

Answer 22

• they are created from plants and waste and can be burnt to produce electricity by heating water, steam turns turbine
• they are fairly reliable, quick to produce, are continually produced and stored as otherwise they cannot respond to immediate demands
• the cost to refine bio-fuel is very high, areas of forest may be cleared to make room to grow them -loss of habitats and decayed vegetation increases methane and carbon dioxide

Question 23

What is wind power, the advantages and disadvantages?

Answer 23

• each wind turbine has an internal generator which turns the blades to turn the generator and produce electricity
• initial costs are quite high, lots are needed to produce a sustainable amount of power, they can spoil views, noisy, wind dependent
• no damage to the environment, cost is minimal to run

Question 24

What are solar cells, advantages and disadvantages?

Answer 24

• solar cells use energy transferred by light to create an electrical current
• no pollution, running costs are minimal
• day dependent, not sustainable for countries that aren’t sunny, initially expensive, relatively small scale

Question 25

What is hydroelectricity, advantages and disadvantages?

Answer 25

• usually involves flooding a valley by building a dam. This means rainwater is caught and allowed out through turbines
• no pollution, reliable all year round so constant source, can immediately respond to increase demand as more water can be let out by turbines, minimal running costs
• initially expensive, flooding can cause loss of habitat, decaying vegetation under the water can produce greenhouse gases

Question 26

What are tidal barrages, advantages and disadvantages?

Answer 26

• big dams built across rover estuaries with turbines in them so when the tide comes, estuary is filled and let out through turbines
• no pollution, pretty reliable, minimal running cost and no fuel cost
• initial cost relatively high, alter habitats, spoil views, affect boat access

Question 27

What may limit the use of renewable energy?

Answer 27

• these new power plants are very expensive
• arguments over where they should be, not near housing in some cases
• less reliable than fossil fuels to meet the demand
• personally, not everyone can afford these changes (e.g. hybrid cars)

Question 28

How can energy be transferred by heating?

Answer 28

By heating - energy transferred from a hot object to a colder one

Question 29

How can energy be transferred by radiation?

Answer 29

by radiation - energy transferred by waves

Question 30

How can energy be transferred electrically?

Answer 30

-Electrically - a charge doing work against resistance like in a circuit

Question 31

What happens when energy is transferred to a ball rolling up a slope?

Answer 31

The ball does work against the gravitational force, so energy is transferred mechanically from the kinetic energy of the to ball to its gravitational potential energy

Question 32

What is the energy transferred from a bat hitting a ball?

Answer 32

• bat has kinetic energy in its store and some if this is transferred mechanically to the ball’s kinetic energy store
• some also transferred mechanically to thermal energy stores
• rest is carried away by sound

Question 33

What is the energy transferred by a rock dropped from a cliff?

Answer 33

• assuming no air resistance, gravity doesn’t work on the rock so it co say toy accelerates towards the ground
• energy transferred mechanically from GPE store to KE store

Question 34

What happens to the energy transfer of a car slowing down?

Answer 34

-cars kinetic energy store is mechanically and then by heating to the thermal energy stores of the car and the road due to friction

Question 35

What happens to the energy transfer of the kettle boiling water?

Answer 35

-energy transferred electrically from the mains to the heating element of the kettle and then by heating to the thermal energy store of the water

Question 36

What energy transfers happen for a girl on a swing?

Answer 36

• originally pushed she has maximum amount of GOPE as she is at her highest point
• as she swings downwards she looses GPE as he height decreases but gains KE due to the forces (weight) acting on her
• as swing rises she looses KE due to a gain in GPE
• throughout swing the back and forth motion gradually decreases in height as some energy dissipates to the surrounds as heat energy due to opposing forces like air resistance

Question 37

Principal throughout the spring?

Answer 37

Total GPE and KE is constant so loss in GPE equals a gain in KE