Chapter 4

Question 1

Give a brief definition about fossil fuels.

Answer 1

A term used to describe non-renewable sources obtained from the remains of dead organisms.

Question 2

Give the definition for power.

Answer 2

The rate at which energy is being transformed, measured in Watts (W).

Question 3

How many types of energy are there?

Answer 3

Kinetic energy, Potential energ(ies), Thermal and Radiated energy.

Question 4

How is kinetic energy calculated? What do the symbols represent?

Answer 4

Kinetic energy = mv2/2 (where m=mass, and v=speed).

Question 5

What is the law of conservation of energy?

Answer 5

Energy cannot be made nor destroyed, but can change from one form to another.
(During energy transformation, the total amount of energy doesn’t change, but gets rearranged).

Question 6

What is meant by ‘ work done ‘ ?

Answer 6

Work done is a measure of an energy/force transferred to an object to move it in a direction.

Question 7

. Why is it important to know about the efficiency of a certain material?
. How’d you measure it?

Answer 7

. It’s important to learn about the efficiency of a substance as it helps us to understand if it’s reliable or not, and how efficient it is.
. There are 2 ways for measuring it:
Useful energy output / Total energy input
OR
Useful power output / Total power input.
By either way,
Useful power output = Force * speed.

Question 8

How is power measured?

Answer 8

Power = amount of energy transformed / time taken.

Question 9

What is work done and energy measured in?

Answer 9

The SI unit for both is Joules (J).

Question 10

. State some typical energy values
. Typical power outputs

Answer 10

. Chemical energy in all the food we eat all day = 11 000 000 J.
Kinetic energy of football when kicked =
50 J.
. A motor = 250 W
. A small car engine = 35000 W
. Large car engine = 150000 W
. Large jet engine = 75000000 W

Question 11

What was known as a `horsepower´ ?

Answer 11

The power unit used in the time of steam engines, 1 hp = 746 Watts.

Question 12

Which type of power plant is the MOST efficient?

Answer 12

The hydro-power plants, as they use dams.

Question 13

What’re the main forms of fossil fuels?

Answer 13

Oil, natural gas and coal which are burnt to produce steam causing the turbines to spin, which turns on the generator and generates electricity.

Question 14

Which component of fossil fuels is known to be the least polluted?

Answer 14

Natural gas, mainly methane, (CH4).

Question 15

Name the main sources of renewable energies.

Answer 15

Windmill, Solar power energy, Geothermal energy, Hydroelectrical and tidal energy and biofuels.

Question 16

How do solar panels work?

Answer 16

They generate electric currents directly from sunlight, trapping those rays. Made up of solar cells (mostly made up of silicon) which has 3 layers.
Top layer (N type) contains silicon and phosphorus which has more electrons than Si, making this layer more conductive.
Bottom layer (P type) contains BOTH silicon and element like Boron which has less electrons than Si, making the layer less conductive.