Bild

Siemens Stiftung

Abnormal audiometric audibility limit

Chart:
Audiometric audibility limit of a person with hearing impairment compared to an intact sense of hearing shows handicap in speech range.

The speech range is that range of frequency and loudness where speech communication usually takes place. Within the audiometric audibility limit it is the kidney-shaped range. In our chart it is coloured blue. When, for example, hair cells are damaged in the inner ear and no longer work, the audiometric audibility limit changes. The speech range is affected.

Information and ideas:
An attempt at comparing charts showing normal hearing and reduced hearing can be done by students individually - as homework. It is useful for testing written expression (English) as well as for testing basic skills from Mathematics or Physics (how to interpret a chart, for example).

Relevant for teaching:
Hearing defects/hearing impairment
How hearing functions
Sound/acoustics

Bild

Siemens Stiftung

Normal audiometric audibility limit

Chart:
Audiometric audibility limit of a person with normal hearing with typical frequency and loudness ranges for speech and music.

The speech range is that range of frequency and loudness where speech communication usually takes place. Within the audiometric audibility limit it is the kidney-shaped range. In our diagram it is coloured blue.

Information and ideas:
An attempt at comparing diagrams showing normal hearing and reduced hearing can be done by students individually - as homework. It is useful for testing written expression (English) as well as for testing basic skills from Mathematics or Physics (how to interpret a diagram, for example).

Relevant for teaching:
Hearing defects/hearing impairment
How hearing functions
Sound/acoustics

Bild

Siemens Stiftung

Magnetic energy

Overview graphic:
Two manifestations of magnetic energy are compared: the magnetic energy of a current-bearing coil and that of an elementary magnet.

Magnetic energy is the energy that is stored in a current-bearing coil in the form of its magnetic field. It is the result of the work that the current has to perform in opposition to the induced voltage (Faraday?s law of induction). Conversely, this magnetic energy is released again in the form of electric current when the magnetic field collapses. Magnetic energy is also stored in a magnetized material. It is equivalent to the work that must be expended in order to align the magnetic dipoles of this material in an external magnetic field. In ferromagnetic materials, the magnetic dipoles align themselves in small zones ("Weiss domains"), even without an external magnetic field. If the Weiss domains are now aligned by an external magnetic field, a permanent magnet is produced.
Incidentally: If a permanent magnet is heated above a critical temperature, it loses its magnetization. The magnetic energy is released as additional heat at this so-called Curie temperature.

Information and ideas:
A simple experiment on magnetization: If you pass a permanent magnet over an iron nail, it magnetizes the nail. What work has to be expended for this, apart from the friction work? Is the permanent magnet or its magnetic energy "used up" in the process?

Bild

Siemens Stiftung

Phase diagram of water

Diagram:
A P-T diagram for pure water. The lines indicate the temperature and the pressure at which the solid, liquid, and vapor phases exist in equilibrium. All three phases exist in equilibrium only at the triple point; otherwise, there are a maximum of two phases.

In addition to the equilibrium curves (melting pressure curve, sublimation curve, vapor pressure curve), the diagram also includes the pressure and temperature data for the melting, boiling, triple, and critical points.
Attention: The axes of the diagram are not shown true to scale.

Information and ideas:
This diagram also reflects the density anomaly of water (lower density in the solid state than in the liquid state): The melting pressure curve shows a negative slope. The reason for the density anomaly is the hydrogen bonds.

Bild

Siemens Stiftung

How long will our energy sources last?

Chart:
A bar chart shows an overview of the remaining years of use of primary energy sources.

Of the fossil energy sources, petroleum will be the first to run out. What is the situation for the other fossil energy sources? Can new technologies delay the point in time when they run out? And is it really true that renewable energy sources never run out?
The time axis has a logarithmic scale.

Information and ideas:
Students learn that the logarithmic scale represents numbers ranging over several powers. More in-depth information regarding how long energy sources will last is provided in the "An overview of energy sources? information sheet.


Dieses Material ist Teil einer Sammlung

Bild

Siemens Stiftung

Steam pressure curve and phase diagram of water

Charts:
The steam pressure curves (p-V diagram) and the phase diagram (p-T diagram) of water are compared.

If you heat water to 100 °C at normal atmospheric pressure, it turns into steam. But what effect does raising or lowering the pressure have on the vaporization temperature?
The answer to this is given by the steam pressure curve (T-curves in the p-V diagram on the left) and the phase diagram (p-T diagram of the right) of the water. Steam pressure is the term for the pressure at which gas and liquid are in equilibrium, i.e. the same number of molecules evaporate as condense back into water. Above the critical temperature (numerical values are given) the water is always gaseous, regardless at what temperature, and it can be treated as a real gas (Van der Waals equation, formula is given). At every temperature below the critical temperature there is a steam pressure for which there is a two-phase zone (liquid and gaseous). In the liquid phase range it is possible to recognize from the steep rise in the curves that liquid substances are barely compressible.
The critical temperature must not be confused with the triple point temperature (see p-T diagram). This characterizes the values of temperature and pressure at which all phases (solid, liquid and gaseous) are present simultaneously.

Information and ideas:
At what temperature does water boil on Mount Everest? So-called "Steam pressure tables" provide information about this. It would also be interesting to refer to the phase transition points as temperature critical points. At the phase transition from liquid to gaseous the energy applied does not initially lead to an increase in temperature. The same applies to the melting of ice. Not until all the water has evaporated or melted does the temperature rise further.

Bild

Siemens Stiftung

;: Chemical energy

Chart:
Chemical energy as binding energy between atoms (as a potential curve in the illustration).

Chemical energy is present both in the bond between atoms and molecules as well as in the potential for chemical bonding. This energy can be released in the form of heat during the bonding process or when those bonds are broken. This "heat of reaction" is also referred to as reaction enthalpy (H). The release of heat (dH < 0) is referred to as an exothermic reaction. An endothermic reaction is when heat is absorbed (dH > 0).
Every mixture of source materials that can react to produce end products can be regarded as a potential source of chemical energy.
Microscopically speaking, this chemical energy can be found in the bonds between individual atoms, as illustrated in the potential curve.

Information and ideas:
Chemical energy is a form of energy that is easy to store - whether in the human body or in batteries. An additional example is hydrogen as a chemical energy store for renewable energy sources.

Bild

Siemens Stiftung

Energy Saving: Energy saving as an energy source

Schematic diagram:
On the basis of selected examples, this overview demonstrates that energy saving itself can be described as an "energy source.?

Five examples from everyday life (electric power and heat generation, power distribution, construction, lighting, and transportation) are used to show how energy saving reduces the consumption of individual energy sources (primary or secondary).

Information and ideas:
Students can look for further examples. What is the significance of energy saving in relation to the general scarcity of resources? Can it be equated roughly with the harnessing of renewable energy sources?


Dieses Material ist Teil einer Sammlung

Bild

Siemens Stiftung

Global primary energy consumption

Chart:
Global primary energy consumption in 2012

Chart:
A bar chart indicates the extent of primary energy consumption in millions of tonnes of oil equivalents (mtoe) of individual regions of the world and their percentage share of global energy consumption.

Information and ideas:
The following questions are good for a short presentation: Who or what is the OECD? What are the objectives of the OECD? Which countries are OECD members?

Using the following source: International Energy Agency (IEA)


Dieses Material ist Teil einer Sammlung

Bild

Siemens Stiftung

Thermal energy

Diagram:
Formulas for the thermal energy of gases and temperature as a function of their molar heat capacity at constant volume.

The thermal or internal energy of a substance is the sum of the kinetic energies of its atoms or molecules. This energy is measurable as temperature. If you supply heat to the substance, the particle speed increases and the temperature rises. In the case of molecular gases, the supply of heat in addition to the translatory motion can excite other forms of motion (rotation and oscillation). This finds expression in the stepped curve of the molar heat capacity (diagram at the right). The molar heat capacity of a substance is the amount of energy required to raise 1 mole of a substance by 1°C. For gaseous substances, the following applies: If the gas particles move only linearly (translation), the amount of heat that is required to raise the gas by 1°C remains constant at 3R/2. In the case of molecular gases, the molecules start to rotate when a specific temperature is reached. In this area (linear increase in the diagram), more energy must be supplied to raise the temperature by 1°C, since the energy goes not only into the translatory motion, but also into exciting the rotation. If all particles are made to rotate, the energy required to raise the temperature by 1°C is again constant at 5R/2. The rise at the point of transition from rotation to oscillation can be explained in a similar way.

Information and ideas:
The overview graphic summarizes the topic of thermal energy using the example of gases. You will find detailed explanations as well as an explanation of the heat in solid bodies in the guideline "What is energy?"