P123 Energy

Question 1

state the equation for work done

Answer 1

work done = force x distance
W = F x s
(J) (N) (m)

Question 2

state the equation for electrical energy

Answer 2

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

Question 3

state the equation for gravitational potential energy

Answer 3

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

Question 4

state the equation for kinetic energy

Answer 4

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

Question 5

state the equation for efficiency

Answer 5

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

Question 6

state the equation for elastic potential energy

Answer 6

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

Question 7

state the equation for power

Answer 7

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

Question 8

state the gravitational field strength on earth

Answer 8

9.8N/kg

Question 9

define internal energy

Answer 9

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

Question 10

define nuclear energy

Answer 10

energy released when atoms either split or fuse together

Question 11

define dissipation

Answer 11

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

Question 12

state the use of lubrication and thermal insulation

Answer 12

• 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

Question 13

describe fossil fuels

Answer 13

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

Question 14

describe nuclear fuel

Answer 14

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 15

describe wind power

Answer 15

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 16

describe solar power

Answer 16

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

Question 17

describe hydroelectric power

Answer 17

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 18

describe tidal power

Answer 18

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

Question 19

describe biofuel

Answer 19

crops are burned for fuel to heat water to steam -> steam turns a turbine to power electricity generator
/ sustainable, reliable, carbon neutral as plants growing take in the CO² produced when burned
X produces greenhouse gas, requires land for crops which reduces land available for food crops

Question 20

describe geothermal power

Answer 20

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 21

describe wave power

Answer 21

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