P123 Energy

Question 1

state the equation for work done

Answer 1

work done (energy transferred) = force x distance
W (E) = F x s
(J) (N) (m)
-> 1 J/s is equal to 1 W

Question 2

state the equation for electrical work

Answer 2

electrical work = potential diff x charge
E = V x Q
(J) (V) (C)

Question 3

state the equation for gravitational potential energy

Answer 3

ΔGPE = mass x gravitational field strength x height
ΔEp = m x g x h
(J) (kg) (N/kg) (m)

Question 4

describe the GP energy store

Answer 4

• energy stored in an object raised above ground
• when mass+ height of object and gravitational field strength increases, its store of GPE increases

Question 5

state the equation for kinetic energy

Answer 5

KE = 1/2 x mass x velocity²
Ek = 1/2 x m x v²
(J) (kg) (m/s)

Question 6

describe the kinetic energy store

Answer 6

• energy stored in a moving object
• transferred into the store when the object speeds up, transferred out when object slows down
• when mass+ speed of object increases, its store of kinetic energy increases

Question 7

state the equation for elastic potential energy

Answer 7

elastic potential energy = 1/2 x spring constant x extension²
Ee = 1/2 x k x e²
(J) (N/m) (m)

Question 8

describe the elastic potential energy store

Answer 8

• energy stored in an object that is stretched/ squashed
• the more it is stretched/ squashed, the greater its store of EPE
  -> providing the object has not exceeded its limit of proportionality

Question 9

name objects which store chemical energy

Answer 9

• foods
• muscles (transferred out when someone pushes something)
• batteries

Question 10

state the equation for efficiency

Answer 10

useful energy output (J) / total energy input (J)

Question 11

state the equation for power

Answer 11

power = energy transferred / time taken for transfer
P = E / t
(W) (J) (s)

Question 12

state the gravitational field strength on earth

Answer 12

9.8N/kg

Question 13

define internal energy

Answer 13

• energy in an object due to movement and position in a gravitational field
• sum of KE and GPE

Question 14

name the energy stores (8)

Answer 14

Magnetic- object affected by magnetic field
Gravitational potential- position in a gravitational field/ height above ground
Electrostatic- object is electrically charged
Thermal- when object has high temp
Nuclear- energy released when atoms split/fuse
Elastic potential- when object is stretched/squashed
Chemical- when chemical reactions takes place
Kinetic- energy due to movement

Question 15

name energy transfers (4)

Answer 15

work has been transferred by..
* heating
* radiation/ waves
* electric current
* work done by forces (eg. mechanical work by humans, against friction)

Question 16

define mechanical work

Answer 16

the amount of energy that has been transferred by a force (Joules)
eg. chemical energy is transferred mechanically by work done by forces to the kinetic energy store of a ball (thrown upwards)+ the arm

Question 17

define nuclear energy

Answer 17

energy released when atoms either split or fuse together

Question 18

define dissipation

Answer 18

when energy is transferred to the thermal store of the surroundings as waste energy

Question 19

state the use of lubrication and thermal insulation

Answer 19

• lubrication - use of oil/grease to reduce friction between two parts therefore reducing unwanted energy transfer as thermal energy
• insulation - using materials with low thermal conductivity to reduce unwanted energy transfer as thermal energy (loft insulation, triple-glazed windows)

Question 20

describe fossil fuels, pros+cons

Answer 20

fuel is burned to heat water into steam -> steam turns turbines to power an electricity generator
/ low cost, reliable as readily available
X non-renewable, produce CO² which is a greenhouse gas that contributes to climate change, burnt coal causes acid rain

Question 21

describe the effect of fossil fuels on global warming

Answer 21

• glaciers/ ice sheets melting- rising sea levels, loss of polar habitats
• rising sea levels- more flooding in low-lying coastal areas, submersion of coastal towns
• extreme weather, change in precipitation patterns
• carbon monoxide/ sulfur dioxide/ soot/ nitrogen oxide - affect human health, acid rain, smog, global dimming

Question 22

describe nuclear fuel, pros+cons

Answer 22

fuel undergoes a nuclear reaction to release thermal energy -> heats water to steam -> steam turns turbines to power an electricity generator
/ generates a lot of energy per kg of fuel, reliable, doesn’t release greenhouse gases
X non-renewable, requires safety measures as radioactivity is dangerous, expensive construction+security costs (from tourists), produces radioactive waste

Question 23

describe wind power, pros+cons

Answer 23

wind turns a turbine which powers an electricity generator
/ sustainable, no pollution, used in remote areas
X unreliable as no energy provided when it’s not windy+ turbines are turned off when too windy as they can break, considered ugly, noisy

Question 24

describe solar power, pros+cons

Answer 24

thermal energy from sun is focused to boil water to steam in a power station / solar panels use thermal energy for heating / photocells convert light to electricity
/ sustainable, no pollution, excess energy from domestic solar panels can be sold back to energy producers, some used in remote areas
X unreliable as no energy produced at night or in bad weather, expensive, only used in desert countries, noisy, ruin landscape

Question 25

describe hydroelectric power, pros+cons

Answer 25

build a dam, river flows over turbines to power generator
/ reliable, sustainable, easily controlled, no pollution
X requires flooding land, destroys local area+habitats, ugly structure

Question 26

describe tidal power, pros+cons

Answer 26

turbine driven with tide movement to power generator
/ reliable, no pollution, sustainable
X ugly, dangerous for wildlife+damages habitats

Question 27

describe biofuel, pros+cons

Answer 27

crops are burned for fuel to heat water to steam -> steam turns a turbine to power electricity generator
/ sustainable, reliable, renewable/ carbon neutral if plants are regrown - take in the CO² produced when burned, can use animal waste
X produces greenhouse gas, requires land for crops which reduces land available for food crops, using wood leads to deforestation

Question 28

describe geothermal power, pros+cons

Answer 28

water is pumped underground to areas which are tectonically active -> water is boiled by heat of the earth -> steam turns turbines to power electricity generator
/ reliable, no pollution
X can only be used in volcanic areas

Question 29

describe wave power, pros+cons

Answer 29

waves drive the turbine which powers the electricity generator
/ sustainable, no pollution
X unreliable as relies on strong waves, ugly, damages habitats

Question 30

name the main uses of energy resources (3)

Answer 30

• transport: mainly oil fuels (petrol, diesel, kerosene), new biofuel or electrically-powered vehicles
• heating: mainly natural gas, wood/ coal/ oil burners, new electric heaters
• electricity generation: UK’s supply comes from many sources, mainly fossil fuels (gas/ coal), nuclear power, renewable sources (mainly wind/ biomass)