IB Physics SL - CHAPTER 8

Specific energy is the measure of the amount of energy per unit mass of a fuel. (Unit: J/kg)

Energy density is the measure of the amount of energy per unit volume of a fuel. (Unit: J/m^3)

Density = Energy density/Specific energy

Represent energy transfers.

A primary energy source is one that is found in the natural environment.

A secondary source is processed or refined primary resources (into useful energy).

A renewable energy source is one that is reproduced at a higher rate than it is consumed.

A non-renewable energy source is one that is not reproduced at a higher rate than it is consumed.

1. Transport

2. Electricity generation

3. Heating

Solar heating panels use thermal radiation to warm water.

Photovoltaic cells use light to create energy.

• Unlimited supply of energy

• Clean to produce the electicity

• Freely available everywhere

• Cheap maintenance

• No fuel is required for energy

• Impacted by poor weather

• Limited efficiency

• Only available during the day

• Requires large investment upfront

• Needs large areas

Control rods: Absorb neutrons.

Moderators: Slows down neutrons.

Shielding materials: Absorb hazardous radiation.

Uranium fuel: Producers heat when reacting.

Water: Turns to steam and turn turbines.

• Extensive reserves of fissionable materials

• Increasingly refine technology available

• No greenhouse gases produced

• A large amount of power is produced

• Hazardous radioactive waste materials produced

• Dangerous if the power plant goes significantly wrong

• Danger of misuse of nuclear material (nuclear bombs)

• Problems with mining fuel

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Boiler: Burns fossil fuels.

Condenser: Cools water.

Fossil fuel: Produces heat when burned.

Water: Turns to steam and turn turbines.

• Extensive infrastructure in place

• High energy density of fuel

• Available energy at any time

• Well-known and developed technology

• Produces greenhouse gases

• Unsustainable

• Produces pollution

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Wind generators: Uses wind to turn turbines.

• Clean energy generation

• Freely available

• Is always sustanable and will never run out

• Not consistent energy production

• Needs favourable local conditions to be placed in windy locations

• Can by visually unappealing

P = 1/2 · pAv^3

Reservoir: Stores large bodies of water high up.

Dam: Holds water in its reservoir.

Control gate: path leading water to turine

• Clean energy generation

• Sustainable

• Can be stored for when needed

• Large areas and changes to the environment are needed

• It relies on suitable locations

• A large initial investment is required

P = mgh/∆t = p∆Vgh/∆t

Conduction is a method of thermal energy transfer that occurs when two solids come in physical contact with one another.

1. Atomic vibrations, or

2. Free electron collisions

Convection is a method of thermal energy transfer that occurs due to the movement of atoms in liquids and gases, resulting from variations in density within the liquid or gas.

1. Convection current

Thermal radiation is a method of thermal energy transfer that occurs by means of electromagnetic radiation normally in the infrared region.

Electric charges within the atoms in a material vibrate causing electromagnetic radiation to be emitted.

A perfect black-body is an object that absorbs all radiation incident on it and does not reflect or transmit any radiation in return.

The formula is:

The formula is:

The solar constant is the amount of solar radiation across all wavelengths that is incident in one second on one square meter of the Earth’s athomosphere at the mean distance of Earth from the Sun.

Albedo, a, is the proportion of radiation incident on and scattered by a given surface.

a = total scattered power/total incident power

Albedo of a planet is the ratio between the total scattered radiation and the total incident radiation of that planet. (Earth = 0.3)

• Time of year

• Latitude (North/South/etc.)

• Terrain

Emissivity, e, is the power radiated by a surface divided by the power radiated from a black body of the same surface area and temperature.

e = power radiated by an object/power emitted by a black body

Most effect

• Carbon dioxide

• Water vapor

Less effect

• Ozone

• Methane

• Nitrous oxides

• Ice and snow will melt (darker surface)

• The solubility of carbon dioxide in the sea will decrease (more carbon dioxide in the atmosphere)

• Surface water will evaporate (more water vapor in the atmosphere)

Power = Area · Intensity · Time · Efficiency