Energy - topic 8 (pg 213-214) paper 2

Question 1

Law of conservation of energy

Energy can be…

Answer 1

stored in different ways and can be transferred from energy store to another

Question 2

Name the main 8 energy stores

Answer 2

chemical
kinetic
gravitational potential
elastic
thermal
magnetic
electrostatic
nuclear

Question 3

Energy transfers

Answer 3

mechanically
electrically
thermally
radiation

Question 4

how do mechanical energy transfer work

Answer 4

by a force moving through a distance

Question 5

how does electrical energy transfers work

Answer 5

by the use of electrical current

Question 6

how does thermal energy transfers work

Answer 6

because of a difference in temperature

Question 7

how does radiation energy transfers work

Answer 7

by waves such as electromagnetic or sound

Question 8

mechanical process become wasteful when..

Answer 8

they lead to a rise in temperature of the surroundings

Question 9

the total energy present in the original stores must be equal to the

Answer 9

energy present in the stores after the transfers

Question 10

you cannot

Answer 10

create or destroy energy

Question 11

efficiency

Answer 11

the measure how much useful energy it transfers in comparison to wasted energy

Question 12

rate of thermal energy transfer through a wall of a house depends on

Answer 12

• the difference in temperature between the interior and exterior
• the thickness of the walls
• the material of which the walls are made from

Question 13

how can you reduce unwanted energy transfers

Answer 13

by thermal insulation and lubricators

Question 14

efficiency formula

Answer 14

efficiency = useful energy transferred by the machine
————————————————————
total energy supplied to the machine x 100%unit

Question 15

power is measured in

Answer 15

watts

Question 16

most machines waste energy as

Answer 16

heat energy

Question 17

Define and name 5 main renewable energy resources

Answer 17

Will no run out, most don’t cause pollution or emit carbon dioxide

• Solar cells
• Bio-fuels
• Hydroelectricity (dam water)
• Wind turbines
• Tidal powers

Question 18

Solar cells

Answer 18

Renewable

• convert solar (sun) energy directly to electricity
• can be used directly to cook food or heat water

Question 19

Bio-fuels

Answer 19

Renewable

- animal or plant matter used to produce thermal energy, electrical energy or power cars

Question 20

Hydroelectricity

Answer 20

Renewable

- generates electricity from water behind a damn flowing down a pipe and turning a turbine to create energy

Question 21

Wind turbines

Answer 21

Renewable

- use kinetic energy from the wind to generate electricity

Question 22

Tidal power

Answer 22

Renewable

- uses the rise and fall of the tide or tidal currents to generate elctricity

Question 23

Define non-renewable energy resources

Answer 23

Non-renewable resources will eventually run out, they are available all the time unlike some renewable resources

Question 24

Nuclear fuels such as uranium are used

Answer 24

• to generate electricity

- as energy sources in spacecraft

Question 25

The fossil fuels are; and are used:

Answer 25

Coal, oil and natural gas - the generate electricity - to power transport - to heat homes and for cooking

Question 26

The use of energy resources has changed over time due to several reasons

Answer 26

World population- in the past 200 years, gone from 1 bil to 7 bil. Development of technology - more vehicles such as cars, planes and trains and other devices require more energy Electrical energy - power stations require fuels in order to generate electricity

Question 27

Trends in world energy uses

Answer 27

- most of the worlds energy uses had =s been fossil fuels - before 1900. biomass in the form of wood was the major source of fuel and its use has remained constant - in recent years, increase in the use of nuclear fuel and hydroelectric power

Question 28

Gravitational potential energy is

Answer 28

the energy possessed by a body due to its heught above the earth.

Question 29

the value of gravitational potential energy stored depends on

Answer 29

- the mass of the body - the gravitational field strength - the height the body is raised

Question 30

change in gravitational potential energy equation

Answer 30

change in gravitational potential energy (J) = mass (kg) x change in gravitational field strength (N/kg) x change in vertical heght (m) ΔGPE = m x g x Δh GPE = kg x N/kg x m

Question 31

What is the gravitational field strength on earth

Answer 31

10N/kg, also can be given in m/s²

Question 32

Kinetic energy is stored in

Answer 32

moving objects

Question 33

kinetic energy equation

Answer 33

``` kinetic energy (J) = 1/2 x mass (kg) x (speed)² (m/s)² KE = 1/2 x m x v² ```

Question 34

Kinetic energy is directly

Answer 34

proportional to the mass of the object: doubling the mass doubles the kinetic energy

Question 35

describe

Answer 35

write facts events or processes accurately