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

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

Answer 2

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 3

what are the main energy sources for:

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

Answer 3

(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 4

pos/neg of:

• fossil fuels

Answer 4

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

Question 5

pos/neg of:

• nuclear power

Answer 5

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 6

how do biofuels work?

Answer 6

• 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 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

state some issues with energy supply

Answer 9

• 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 10

what is a problem with renewable energy sources?

Answer 10

• 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 11

How many milliseconds in one second?

Answer 11

1000

Question 12

in the national grid electrical power is transferred at ….. voltages from ……. …….. and then transferred at …….. ….. in each locality for domestic use

Answer 12

high
power stations
lower voltages

Question 13

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

Answer 13

the potential difference as power is transferred from power stations

Question 14

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

Answer 14

• 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 15

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

Answer 15

the total power transferred

Question 16

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

Answer 16

Vp x Ip = Vs x Is

Question 17

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

Answer 17

P = I^2 x R

Question 18

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

Answer 18

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

Question 19

difference between direct and alternating current

Answer 19

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

Question 20

what is a source of DC current?

Answer 20

battery, cells

Question 21

name the colour of

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

Answer 21

a) brown
b) blue
c) green and yellow

Question 22

function of

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

Answer 22

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 23

potential difference between

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

Answer 23

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

Question 24

what does it mean when an appliance is live?

Answer 24

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 25

danger of providing connection between live wire and earth wire?

Answer 25

current can flow directly to the ground constantly
- may result in fire or shock on the floor

Question 26

explain the protection offered by insulation of devices

Answer 26

• 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