Energy - Introduction

Question 1

What is the SI unit for energy?

Answer 1

Joule (J)

kJ - kilojoule, MJ - megajoule and GJ - gigajoule are also commonly used

Question 2

List some forms of energy in the world

Answer 2

• Mechanical energy
• Heat/thermal energy
• Electrical energy
• Chemical energy
• Kinetic energy
• Nuclear energy
• Light energy
• Sound energy
• Solar energy
• Gravitational potential energy

Question 3

Forms of energy can be classified into 2 groups. State these 2 groups:

Answer 3

1. Kinetic energy - Energy of movement
2. Potential energy - Stored energy

Total energy = Kinetic energy + Potential energy

Every object has both kinetic and potential energy

Question 4

What are some sources of energy?

Answer 4

Sun
* Primary source of energy in our solar system

Fossil Fuels
* Coal
* Petroleum (oil)
* Natural Gas

Biomass
* Wood
* Plants and animals used as food
* Biogas
* Bioethanol
* Biodiesel

Wind energy
Hydro energy
Tidal energy
Radioactive decay

Question 5

Describe how Fossile Fuels become a source of energy:

Answer 5

• Photosynthesis in plants occurs due to solar energy
• Photsynthesis converts light to chemical energy
• This becomes stored in dead animal that undergo high pressure, compression and heat to become fossil fuels.

Question 6

Describe how Biomass becomes a source of energy

Answer 6

• Solar energy from sun is captured and converted to chemical energy and is stored.
• Can be store din plants or in animals.
• When eaten or burnt, releases energy

Question 7

Describe how energy is lost or transformed

Answer 7

• Energy is never lost
• It is only transferred to other mass or transformed to different form of energy
• Energy present before and after transformation is equal

Question 8

What is energy efficiency?

Answer 8

A measure of how much energy ends up in the form you want

Question 9

Give the formula for energy efficiency

Answer 9

% energy efficiency = (useful energy x 100) / Total energy input