Energy sources and Transfer of Energy

Question 1

What is work?

Answer 1

The product of force and distances moved in the direction of the force

Question 2

Formula and unit for work done

Answer 2

Work done = force x distance moved along the line of action of the force
Unit: Nm or J

Question 3

A man pressed his hands against a strong wall of height 4m with a force of 30N. Calculate his work done

Answer 3

Work done = force x displacement

30 x 0= 0J

Question 4

What is energy?

Answer 4

Energy is the ability to do work

Question 5

What is energy equal to?

Answer 5

Energy = work done

Question 6

What is the unit of energy?

Answer 6

J or KJ

Question 7

How many joules is 1KJ?

Answer 7

1 KJ —-> 1000J

Question 8

Forms of energy (8)

Answer 8

1) Light energy
2) Heat energy
3) Electrical energy
4) Potential energy
5) Sound energy
6) Chemical energy
7) Kinetic energy
8) Wind energy

Question 9

Sources of energy (6)

Answer 9

1) Solar energy
2) Biomass
3) Geothermal
4) Fossil fuels
5) Batteries
6) Nuclear energy

Question 10

Types of energy sources (2)

Answer 10

Renewable

Non-renewable

Question 11

Define renewable energy sources and examples

Answer 11

It is always available. eg. solar, wind, falling water, biomass, geothermal, tidal, wave, hydro-electricity

Question 12

Define non-renewable energy sources and examples

Answer 12

It will finish eventually. eg. fuel, petrol, kerosene (fossil fuels), nuclear

Question 13

Advantages of using renewable energy (4)

Answer 13

1) It is always available
2) It is free
3) Available locally
4) Some of them do not cause pollution

Question 14

What is the principle of conservation of energy?

Answer 14

Energy can neither be created nor destroyed in any process, it can be converted from one form to another.
(Total amount of energy remains constant)

Question 15

What is kinetic energy?

Answer 15

The energy possessed by any moving object

Question 16

Formula and unit for kinetic energy

Answer 16

Kinetic energy = 1/2 mass velocity^2
Kinetic energy = 1/2mv^2
Unit: J

Question 17

What is gravitational potential energy?

Answer 17

The energy possessed by any object due to its height above ground

Question 18

Formula and unit for gravitational potential energy

Answer 18

G.P.E = mass x gravity x height
G.P.E = mgh
Unit: J

Question 19

Describe chemical energy

Answer 19

This form of energy is usually stored in food, fossil fuels, batteries and in the re-grouping of atoms during chemical reactions

Question 20

Describe hydro-electric generation

Answer 20

Water, in lakes on high grounds, stores large amount of gravitational potential energy which is converted to kinetic energy when flowing through pipe to turn the turbines and thus generating electricity

Question 21

Describe geothermal energy

Answer 21

Large amounts of heat is produced due to nuclear reactions deep in the Earth. Water is channelled through pipes in the hot regions which in turn gets heated until boiling takes place to produce steam. The steam pressure is used to drive the turbines to generate electricity

Question 22

Describe wind energy

Answer 22

Wind farms are set up in windy regions. The kinetic energy of the wind acts on the long blades of the turbines to generate electricity

Question 23

Describe solar energy

Answer 23

As a product of nuclear fusion of hydrogen nuclei into helium nucleus, heat energy from the sun reaches the Earth’s surface in the form of electromagnetic waves

Question 24

How is heat energy from sunlight used? (2)

Answer 24

1) Solar panels absorb the heat from the sunlight to heat water which is then stored in an insulated tank
2) Photovoltaic cells are installed on the roof of houses and commercial buildings to produce their own electricity

Question 25

Describe nuclear fission

Answer 25

Common in a nuclear reactor of nuclear power station. This reaction can be controlled. A large nucleus is split into two or more light nuclei of comparable sizes and large amounts of heat energy is released

Question 26

Describe nuclear fusion

Answer 26

It occurs in the sun. Two light nuclei of hydrogen fuse together to produce a heavy nucleus of helium and huge amount of heat energy produced. A very high temperature is needed for nuclear fusion to occur.

Question 27

During a nuclear reaction where is the large amount of heat energy derived from?

Answer 27

A mass defect

Question 28

What is power?

Answer 28

The rate at which work is done

Question 29

Formulas and units for power

Answer 29

Power = work done ÷ time
OR
Power = energy ÷ time
Units: J/s or W

Question 30

Formula for % efficiency

Answer 30

% efficiency = output power ÷ input power x 100

Question 31

Formula for efficiency

Answer 31

Efficiency = output power ÷ input power

Question 32

What are possible reasons for power waste? (2)

Answer 32

1) Loss of energy due to friction

2) Work done against air resistance

Question 33

What are some common energy conversions? (4)

Answer 33

1) Filament lamp
2) Hair dryer
3) Fluorescent lamp
4) Coal-fired power station

Question 34

Advantages (2) and disadvantages (2) of solar energy

Answer 34

Advantages: No pollution. Renewable
Disadvantages: Expensive. Limited use in certain areas without continuous sun

Question 35

Advantages (1) and disadvantages (4) of nuclear energy

Answer 35

Advantages: Large amount of energy is released
Disadvantages: Expensive to set up. Uses high technology. High level of precautions. Danger from radioactive radiations that may cause cancer

Question 36

Advantages (2) and disadvantages (3) of biofuel

Answer 36

Advantages: Renewable. Easy to produce
Disadvantages: Causes pollution in the atmosphere. Disruption of scenery. Large plot of land is required for disposal of wastes for decomposition