1: Energy

Question 1

thing can only do work if they…

Answer 1

contain a store of energy

Question 2

what is a kinetic energy store?

Answer 2

the energy of a moving object

Question 3

what is a gravitational potential energy store?

Answer 3

the energy something gains when you lift it up; lost when it falls

Question 4

what is an elastic potential energy store?

Answer 4

the energy of a stretched spring or elastic band

Question 5

what is an electrostatic energy store?

Answer 5

the energy due to the force of attraction / repulsion between two charges

Question 6

what is a magnetic energy store?

Answer 6

the energy due to the force of attraction / repulsion between two magnets

Question 7

what is a chemical energy store?

Answer 7

the energy contained in a chemical substance

Question 8

what is a nuclear energy store?

Answer 8

the energy contained within the nucleus of an atom

Question 9

what is a thermal energy store?

Answer 9

the energy something has due to its temperature / state

Question 10

in what four ways can energy be transferred?

Answer 10

mechanically - when a force acts on a body, energy transferred between two stores
electrically - electricity can transfer energy from a power source, delivering it to components in a circuit
heating - thermal energy transferred by conduction, convection and thermal radiation
radiation - light and sound carry energy and so can transfer it

Question 11

what is the conservation of energy?

Answer 11

energy cannot be created or destroyed - can only be transferred from one store to another

Question 12

what is energy like in a closed system?

Answer 12

total amount of energy is constant

Question 13

what is the diagram to show energy changes?

Answer 13

original energy store –> new energy store –> final energy store

Question 14

what energy does an object have when it’s moving?

Answer 14

kinetic energy

Question 15

what’s the equation for kinetic energy?

Answer 15

KE (J)= 1/2 x mass (kg) x speed squared (m/s)

Question 16

what energy does an object have when it is raised above ground level?

Answer 16

gravitational potential energy - energy due to height in a gravitational field

Question 17

what’s the equation for gravitational potential energy?

Answer 17

GPE (J) = mass (kg) x height (m) x gravitational field strength (N/kg)

Question 18

what energy does a stretched spring have?

Answer 18

elastic (store) - work done on the spring to stretch/compress is equal to the amount of energy stored

Question 19

what’s the equation for elastic potential energy/work done on a spring (assuming the limit of proportionality has not been exceeded)?

Answer 19

energy (J) = 0.5 × spring constant (N/m) × extension squared (m)

Question 20

what is specific heat capacity?

Answer 20

the amount of thermal energy required to raise the temperature of 1kg of that substance by 1 °C.

Question 21

what is the equation to calculate the amount of thermal energy needed to raise the temperature of a given mass of material by a different amount?

Answer 21

change in thermal energy (J) = mass (kg) × specific heat capacity (J/kg °C) × change in temperature (°C)

Question 22

describe the experiment to determine the specific heat capacity of a substance

Answer 22

start by attaching power supply to heater & inserting heater and thermometer into a block of substance (has weight of 1kg) and measure initial temp. of substance.
turn on power supply & start stop-clock.
whilst the power supply is on take several periodic measurements of voltage & current, & calculate an average of these values.
after 5 minutes switch off the power supply, stop the stop-clock & leave apparatus for a few more minutes.
monitor thermometer & make a note of highest temp. reached.
calculate the rise in temperature.

Question 23

heat supplied to a substance can be calculated using the equation:

Answer 23

energy (J) = current (A) × voltage (V) × time (s)

Question 24

what is the issue with the practical?

Answer 24

not all of heat supplied by the heater will go into substance – some will go into surroundings & substance will also lose heat whilst it is being heated; means value for the heat added will be too great which means calculated specific heat capacity will be too great

Question 25

what is power?

Answer 25

the rate at which energy is transferred / work is done

Question 26

what is the equation to calculate power?

Answer 26

power (W) = work done (J) / time taken (s)

Question 27

two identical cars accelerating to the same final speed will gain the same amount of energy. if one of them reaches that speed sooner, who has the greater power?

Answer 27

the faster one

Question 28

what (3) forms of energy can dissipate?

Answer 28

heat, light, sound

Question 29

if energy dissipates, what does this mean?

Answer 29

becomes v. difficult to gather the energy back together again; so energy becomes less useful - wasted

Question 30

give an example of a closed system and how the net energy does not change.

Answer 30

a gas cooker, heating a pan of water, takes energy from chemical store of gas and transfers it to thermal store of water

Question 31

in what two ways can you reduce energy loss?

Answer 31

reduce amount of unwanted energy produced; prevent energy from dissipating

Question 32

how can mechanical loss of energy, due to friction be reduced?

Answer 32

amount of friction reduced, less energy will be transferred into heat - lubricate the parts that rub together

Question 33

how can you stop/reduce loss of heat energy?

Answer 33

surround something with insulation

Question 34

what does the effectiveness of insulation depend on?

Answer 34

how well the insulation conducts heat; how thick the insulation is

Question 35

describe the practical to test the effectiveness of different insulations.

Answer 35

several identical containers are taken and insulated in different ways- one container should usually be left uninsulated to act as a control beakers are then filled with equal quantities of boiling water & temp. constantly monitored using thermometer once the water in a beaker reaches a certain temp. (e.g. 90 °C) a stopclock is started for each beaker. temp. readings are taken at regular intervals (e.g. every minute) for a fixed amount of time (e.g. 20 mins) a graph can then be plotted showing how the temperature of each beaker (y-axis) changes with time(x-axis).

Question 36

what is the efficiency of a system?

Answer 36

the proportion of energy that ends up in the intended form (useful energy)

Question 37

what is the equation for calculating efficiency?

Answer 37

efficiency = useful output energy transfer / total input energy transfer OR efficiency = useful power output / total power input efficiency usually given as no. between 0-1 or as a %

Question 38

describe ways you can improve the efficiency of a device.

Answer 38

have to reduce the amount of unwanted energy that is produced: to reduce friction and therefore heat energy: add bearings to prevent components from directly rubbing together; lubricating parts to reduce resistance and therefore heat energy: use lower resistance parts; lower the current to reduce the amount of heat produced.

Question 39

what is the definition of an energy resource?

Answer 39

large banks of energy that can be transferred into a form that can be used by society

Question 40

describe how fossil fuels can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 40

burning fossil fuels produces steams, which can turn turbines; non-renewable; pros: reliable, can produce large amounts of energy in fairly short notice; cons: produces significant ghgs and pollution

Question 41

describe how nuclear fuel can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 41

nuclear fuel is reacted, producing heat which creates steam to turn turbines; non-renewable; pros: reliable, produces no ghgs or pollution, large about of energy from small amount of fuel; cons: produces toxic radioactive waste that can take thousands of years to decay

Question 42

describe how bio-fuels can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 42

plant matter, ethanol or methane can be produced and used as a fuel in place of fossil fuels; renewable; pros: CO2 produced whilst burning is balanced by CO2 absorbed whilst producing; cons: can take up a lot of land and consume resources that are needed for food production

Question 43

describe how wind can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 43

wind turbines can be used to produce electricity; renewable; pros: no ghgs or pollution produced, land can still be used for farming; cons - not reliable, noisy, ugly, not suitable everywhere

Question 44

describe how hydroelectricity can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 44

uses the GPE of water stored in reservoirs to turn turbines which generates electricity; renewable; pros: reliable, can produce large amount of energy at short notice, no pollution or ghgs; cons: can involve flooding areas, destroying wildlife habitats

Question 45

describe how tidal power can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 45

a dam is used to trap seawater at high tide and can then be released through a turbine, generating electricity, renewable; pros: predictable, large amount can be produce at regular intervals; cons: very few suitable locations, can cause environmental harm to sea life

Question 46

describe how geothermal energy can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 46

heat from underground can be used to create steam which spins turbines to generate electricity; renewable; pros: reliable, stations are usually small; cons: can lead to release of harmful gases underground, few suitable locations

Question 47

describe how solar power can be used as an energy resource, whether it is renewable or not, and the pros and cons.

Answer 47

photovoltaic cells can use light to create electricity; thermal radiation from the sun can be used to warm water passing through black pipes; renewable; pros: no ghgs or pollution produce, good for producing energy in remote locations; cons: not reliable, solar farms use up a lot of farmland

Question 48

what is meant by a renewable energy resource?

Answer 48

it is replenished at a faster rate than the rate at which it is being used; cannot run out

Question 49

what is meant by a reliable energy resource?

Answer 49

one that can produce energy at any time

Question 50

why is carbon neutral energy resources not as widely used as hoped?

Answer 50

lack public support, reliability or cannot produce sufficient energy to meet our needs

Question 51

how has energy slowly been shifted to cleaner technologies?

Answer 51

government grants - encouraged development of wind & solar farms coal - gradually replaced with cleaner natural gas more education on different resources

Question 52

how can we further reduce CO2 emissions?

Answer 52

more nuclear power stations will be needed to replace existing fossil fuel stations; develop a way of storing energy from unreliable sources (such as solar and wind)