Energy - Topic 1

Question 1

what is a system

Answer 1

an object or group of objects

Question 2

what happens when a system changes?

Answer 2

energy is transferred, can be transferred into or away from system, between different objects in the system or between different energy stores

Question 3

what are the 8 energy stores

Answer 3

-thermal
-kinetic
-gravitational potential
-elastic potential
-chemical
-magnetic
-electrostatic
-nuclear

Question 4

How can energy be transferred?

Answer 4

mechanically - by a force doing work
electrically - work done by moving charges
by heating
by radiation

Question 5

energy transfer of boiling water in kettle

Answer 5

energy transferred to water by heating, into the waters thermal energy store causing temp of water to rise.

Question 6

what is the specific heat capacity of a substance?

Answer 6

the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree.

Question 7

units of specific heat capacity

Answer 7

joules/degrees Celsius/kilogram

Question 8

what is the conservation of energy?

Answer 8

energy is never created or destroyed only transferred.

Question 9

what is dissipated energy

Answer 9

energy that is being stored in a way that is not useful, sometimes called wasted energy

Question 10

what is a closed system

Answer 10

systems that where neither matter nor energy can enter or leave. the net change in the total energy of a closed system is always 0

Question 11

definition of power

Answer 11

the rate of energy transferred or the rate at which work is done.

Question 12

unit of power

Answer 12

watts

Question 13

two motors lift the same mass through the same height. motor a does this in half the time of motor b which motor dissipates the most energy?

Answer 13

motor a, the energy transferred is the same but the time taken is less, p=e/t

Question 14

describe energy changes when a ball is thrown upwards then returns to its starting position.

Answer 14

• upwards KE is converted to GPE
  -Peak: Maximum GPE no KE
  -downwards GPE converted to KE

Question 15

examples of chemical energy stores

Answer 15

-food
-fuel
-batteries

Question 16

describe energy changes in a filament light bulb

Answer 16

-electrical energy transferred into heat and light energy
-light energy is useful, heat energy is waste energy.

Question 17

how can the efficiency of a system be increased?

Answer 17

-reducing waste output (by using lubricant or thermal insulation)
-recycling waste output

Question 18

what is conduction?

Answer 18

the process where vibrating particles transfer energy to neighbouring particles.

Question 19

do double glazed windows have higher or lower thermal conductivity than single glazed?

Answer 19

lower meaning less energy is transferred though them

Question 20

what factors effect the rate of cooling a building

Answer 20

-thickness of the walls
-thermal conductivity of the walls

Question 21

three methods of reducing heat loss from a building

Answer 21

-double glazing
-loft and wall insulation
-thicker walls

Question 22

how can the efficiency of a mechanical machine with moving parts be improved

Answer 22

lubricate any moving parts to reduce the friction and therefore reduce energy loss due to heating

Question 23

what is a non-renewable energy source? Give examples.

Answer 23

• they will run out one day
  -cause damage to environment
  -e.g coal, oil, natural gas

Question 24

what is a renewable energy source? give examples

Answer 24

-will never run out can be renewed as they are used.
-don’t provide as much energy and some are unreliable because they depend on the weather.
-e.g sun, wind, bio-fuels,tides and geothermal

Question 25

environmental impacts of burning fossil fuels

Answer 25

-carbon dioxide contributes to the green house effect and cases global warming. - sulphur dioxide leads to acid rain which can damage buildings and crops

Question 26

3 advantages of using fossil fuels as energy sources

Answer 26

-reliable: not dependant on external factors -can produce large amounts of energy for a given quantity. -still relatively abundant so cost effective.

Question 27

two disadvantages of using renewable energy sources to generate power.

Answer 27

-output is often determined by external factors (e.g wind) so supply uncertain. -generating power through other means is often more efficient and economically beneficial.

Question 28

three advantages of nuclear power

Answer 28

- very large amounts of energy for relatively small quantities of fuel. - don't release greenhouse gases so don't contribute to climate change. -low fuel cost

Question 29

three disadvantages of nuclear power

Answer 29

- produces nuclear waste which is harmful to humans and must be stored safely for centuries. - non- renewable energy source - risk of nuclear accidents which have fatal consequences on humans and environment.

Question 30

how does hydroelectric power produce energy?

Answer 30

- rain water collects behind a dam - when this water is released it is used to turn a turbine. - This turbine turns a generator which produces electricity.

Question 31

disadvantages of hydroelectric power

Answer 31

- dam may cause flooding - it can cost a lot to install the required infrastructure

Question 32

disadvantages to biofuels

Answer 32

- when plants are burned they relsease co2 - in order to grow biofuels you need to destroy land this causes problems because the land could have been a natural habitat or it might have involved burning or destroying plants which releases co2 - growing biofuels reduces land available to grow food.

Question 33

advantages of tidal energy sources

Answer 33

- don;t produce greenhouse gases. - reliable as tides happen twice a day - cheap to run as tides are natural.

Question 34

advantages of solar pannels

Answer 34

-don't cause harm to the environment - renewable energy source - can be used in remote areas where other types of energy are less acsessable.

Question 35

what is the definition of power?

Answer 35

-the rate at which energy is transferred or the rate at which work is done.

Question 36

equation for kinetic energy

Answer 36

0.5 x mass x (speed)2

Question 37

equation for elastic potential energy

Answer 37

0.5 × spring constant × (extension)2

Question 38

equation for gravitational potential energy

Answer 38

mass × gravitational field strength × height

Question 39

equation for change in thermal energy

Answer 39

= mass × specific heat capacity × temperature change

Question 40

give two equations for power

Answer 40

energy transferred/time -p = e/t and work done/time - p=w/t

Question 41

describe energy transferrs for a bungee jumper

Answer 41

- when falling the GPE is converted to KE of the jumper. - As the chord tightens, KE is converted and stored as Elastic potential Energy. - At the lowest point the jumpers initial GPE = The EpE store in the chord

Question 42

Explain why the bungee jumper slows down as the chord begins to stretch

Answer 42

-Kinetic energy decreases since it is converted to elastic potential energy. - since KE is proportional to (velocity)2 as KE decreases so does velocity

Question 43

give 2 equations to calculate efficiency

Answer 43

- =useful power output energy transfer/ total input energy transfer. - = useful power output/total power output.