P8.2 - Powering Earth

Question 1

describe 2 examples of non-renewable energy sources (and how they work)

Answer 1

fossil fuels - burned to heat up water within a power plant

nuclear fuel - radiation released also heats up water

Question 2

what are the steps within a power plant to produce electricity?

Answer 2

fuel (nucleur/fossil) causes heat to be generated
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heat causes water to turn to steam
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steam turns the turbine
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turbine turns the generator
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generator produces electricity

Question 3

describe 5 types of renewable energy sources (how they work)

Answer 3

biofuel - burning organic material as fuel

wind - using wind to turn turbines (instead of steam)

hydroelectricity - controlling the water falling and it turns the turbine = electricity

tides - similar as hydroelectric (but the sea coming in and out)

solar - using the sun’s energy to generate electricity/heat a house

Question 4

what are the main energy sources for:

(a) transportation
(b) heating
(c) generating electricity

Answer 4

(a) - fossil fuels (crude oil
- biofuels (bioethanol)

(b) - fossil fuels (for heating up the boiler)
- solar heating (or thermal solar)

(c) - mainly coal (36%)
- gas (27%)
- nuclear (20%)
- renewable (14.9%)

Question 5

what are the two types of solar panels?

Answer 5

1) solar cells (photovoltaics) - convert sunlight energy to electrical energy
2) solar panels - convert sunlight to heat energy for heating

Question 6

pos/neg of:

• fossil fuels

Answer 6

P - reliable source of energy (will always burn)
- cost effective (not too expensive to set up)
N - releases greenhouse gases
- non renewable

Question 7

pos/neg of:

• nuclear power

Answer 7

P - extremely energy dense (produced x6000 more energy than fossil fuels
- no greenhouse gases

N - radioactive waste hard to dispose of

• very dangerous (if explodes is disasterous)
  - non renewable

Question 8

how do biofuels work?

Answer 8

• fuel comes from a recently living/living organism (gas from manure, sugar cane, ethanol)
• carbon neutral (CO2 released when burning is reabsorbed when new plants grow)
• does release CO2, but no NET RELEASE of greenhouse gases in the atmosphere *

Question 9

how did the industrial revolution affect out use of energy resources?

Answer 9

• increased use of coal (machines in factories + steam trains)

Question 10

how has new transport (cars + planes) changed our use of energy?

Answer 10

from around 1920, more increase in oil (for cars and planes)

Question 11

what energy supply has remained relatively constant?

Answer 11

biofuels (trees)

Question 12

state some issues with energy supply

Answer 12

• as developing countries become more wealthy, they would require more energy as well
• fossil fuels are finite (and hard to reach as it is becoming more scarce)
• burning fuels produces greenhouse gases (climate change)

Question 13

what is a problem with renewable energy sources?

Answer 13

• they can be expensive to set up (and more pollution may happen when constructing it)
• so it needs to last long enough to produce enough energy to counter that + its cost to set up

Question 14

How many milliseconds in one second?

Answer 14

1000

Question 15

recall that, in the national grid,

Spec

Answer 15

recall that, in the national grid, electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use

Question 16

what are step-up and step-down transformers used to change (and when)?

Answer 16

the potential difference as power is transferred from power stations

Question 17

explain how the national grid is an efficient way to transfer energy

Answer 17

• high voltages in power lines, which reduces current flowing through wires
• this reduces energy lost to the surroundings
• and so transfer of energy is more efficient

Question 18

what remains constant when a potential difference is increased/decreased from a transformer?

Answer 18

the total power transferred

Question 19

equation to calculate step-up/step-down transformer?

Answer 19

Vp x Ip = Vs x Is

Question 20

how to calculate power (in terms of current and resistance)?

Answer 20

P = I^2 x R

Question 21

in terms of the domestic supply in the UK 
what is the: 
a) potential difference 
b) type of current
c) frequency

Answer 21

a) 230V
b) ac current
c) 50Hz

Question 22

difference between direct and alternating current

Answer 22

• AC’s potential difference continuously switches, as does its direction of current
• DC has a fixed (positive) amount

Question 23

what is a source of DC current?

Answer 23

battery, cells

Question 24

name the colour of

a) live wire
b) neutral wire
c) earth wire

Answer 24

a) brown
b) blue
c) green-yellow

Question 25

out of the live, neutral and earth wire

which one is the odd one out and why?

Answer 25

earth wire, as it is not connected to the mains (connected to a pole in the ground outside)

Question 26

function of

a) live wire
b) neutral wire (and how)
c) earth wire (and how)

Answer 26

a) carries voltage from mains to appliance
b) completes the circuit by providing a path back to the electrical panel
c) prevents appliance being live, has low resistance so current goes from casing through earth wire into ground

Question 27

potential difference between

a) live and neutral wire
b) live and earth wire
c) neutral and earth wire

Answer 27

a) 230v
b) 230V
c) 0 V

Question 28

what does it mean when an appliance is live?

Answer 28

live wire becomes loose and touches the metal casing, so then current flows on metal casing/surface of appliance, and if you touch it a current flows through you

Question 29

danger of providing connection between live wire and earth wire?

Answer 29

they would have such a great potential difference between them that a large current would be created which can provide a lethal shock to the person

Question 30

explain the protection offered by insulation of devices

Answer 30

• case can be made of plastic
• so no current can flow through case to you
• called ‘double insulation’
• so an earth pin is not necessarily needed