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Sound propagation: glass pairs

Graphic:
Why does a second glass connected to the first glass with a wire vibrate when we hit the first glass?

This experiment makes it clear that sound is conducted via solid bodies. The glass starts to vibrate when it is rubbed, the wire conveys the vibrations to the second glass.
It must be remembered that the vibrations of the second glass only occur if the glasses have the same pitch level when they are struck or rubbed (use water to adjust levels if necessary)!
Close observation will show that even the water in the second glass starts to vibrate.

Information and ideas:
Setting up the experiment: Two glasses are put at a small distance from each other. A knitting needle or something similar is laid over the two glasses.
Using a moist finger, rub the first glass gently along its rim. A sound is produced, and after a short time the needle begins to vibrate on the second glass as well.

Relevant for teaching:
Acoustic phenomena
Sound/acoustics: parameters
Vibrations and waves

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Sense organs stimuli

Photo:
At a fair, all sorts of stimuli affect our senses, for example, the smell of candy floss, the bright lights of the roundabouts etc.

If all our senses are attracted at the same time with the same degree of intensity, as at a fair, it can be a very pleasant experience but it can also be a strain.

Information and ideas:
The students can report on their own experiences, for example, what can I smell, see and hear at a fair?
What are the typical smells, tastes and sounds associated with Christmas?

Relevant for teaching:
Structure and function of a sense organ
Reception of stimuli and processing of information
Senses discover the environment

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Sense organ skin - sense of touch and of feel

Photo:
The skin as sense organ. A gigantic organ which we use to touch and to feel.

The biggest organ in the human body is the skin.
A twelve-year-old has an amount of skin equivalent to about 20 A4 pages.
The skin has several tasks:
To begin with, to protect against external influences; it can heal itself in the event of minor injuries. And then it is responsible for touching and feeling. We can distinguish between six different sensations: touch, pressure, pain, tension, vibration and temperature.

Information and ideas:
What sorts of things can I feel? Here, it is a good idea to prepare a box full of materials which can be recognised by touching and feeling them.

Relevant for teaching:
The human body
Structure and function of a sense organ
Reception of stimuli and processing of information
Senses discover the environment

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Outer ear section - labeling arrows

Unlabeled graphic:
The graphic is a section view of the entire ear showing all parts belonging to the outer ear. These parts are highlighted in color.

The outer ear consists of the pinna and the ear canal. The ear canal ends at the eardrum.
In the membranous wall of the ear canal there are glands which produce cerumen (earwax). At the edge of the ear canal there are some small hairs, hair follicles, which serve as protection against foreign bodies.

Information and ideas:
Helpful to distinguish outer, middle and inner ear.
Can be used, for example in a worksheet, for work together in class with the digital projector, as overhead transparency.

Relevant for teaching:
The human body
Structure and function of a sensory organ

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Muscle power

Photo:
Two people jogging.


Information and ideas:
An example of the process whereby chemical energy is converted into mechanical energy.

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Loudspeaker

Photo:
The loudspeaker demonstrates the principle of electroacoustic sound transduction. See the video "Sound emission at the loudspeaker?.

The pitch-frequent alternating current supplied by an amplifier flows through a coil in the loudspeaker. In so-called dynamic loudspeakers, this coil is in a ring-shaped permanent magnetic field. The coil is connected to a diaphragm. Through the passage of the alternating current, forces now begin to have an effect on the coil which is moved to and fro in time with the pitch frequency. The diaphragm is moved and transmits its vibration to the air, the sound is emitted.

Information and ideas:
The process of electroacoustic sound transduction can be explained very well to the students with the help of a technical device that is familiar to all of them. Furthermore, the production and propagation of sound waves - important in human physiology for hearing and speaking - can be shown.

Relevant for teaching:
Communication and understanding
Vibrations and waves
Acoustic phenomena

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Lightning - electrical energy from the sky

Photo:
Bolt of lightning between the Earth and clouds - an excellent example of electrical energy in nature.

Rising streams of air generate electricity from mechanical energy by means of friction in the form of electrically charged clouds, up to a charge of 20 ampere-seconds (As). If the voltage difference between the storm cloud and the Earth is greater than 100 million V, a powerful discharge will occur as an electric arc. Because the discharge takes place within fractions of a second, high currents of up to 100,000 A can occur. For example, at a charge of 20 As and a discharge time of 0.4 ms, the current is 50,000 A. At this current, the power of a lightning bolt is 5 terawatts (TW). One TW equals one billion watts. Energy totaling 560 kWh is released in the process.

Information and ideas:
For further study, the physics of the gas discharge could be discussed. Another interesting exercise is to calculate the energy content of a bolt of lightning and to compare it with the calorific value of gasoline. What amount of gasoline corresponds to the energy of a bolt of lightning? Another example of the occurrence of electrical energy in nature is the electric eel, which produces electrical energy from a biochemical reaction.

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The Ear, Hearing and Hearing Impairment: Hearing

Photo:
A girl holds her open hand up to her ear to signalise that she is listening. Introduction to the topic "hearing" but also to "listening".

We use our ears to hear with. The only visible part of the hearing organ is the pinna. It collects the sound and conducts it into the ear canal. If somebody wants to understand better, they automatically hold their hand up to the ear to increase the size of the funnel. That has no immediate effect but has, in the meantime, become a sort of automatic gesture.

Information and ideas:
Introductory picture to the subject "Hearing" and into the discussion of the hearing process. What happens after the sound is picked up by the pinna?

Relevant for teaching:
The human body
Structure and function of a sensory organ
Reception of stimuli and transmission of information

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;: Echolocation with dolphins

Graphic:
Dolphins use the echo under water to locate other fish as prey.

Just like a bat, a dolphin can recognize from the echo whether the prey is nearby or not. It produces clicks and whistling noises under water. If it has discovered something of interest, the dolphin will move closer and "click" more quickly. This gives it an exact acoustical picture of its surroundings.

Information and ideas:
Based on the phenomenon of an echo, this graphic can show how animals use the echo to find prey.

Relevant for teaching:
Functions of the senses
Acoustic phenomena
Sound/acoustics: hearing range, hearing frequency limit, parameters
Vibrations and waves

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Ticking grandfather clock

Recording:
The ticking of a clock, for example, a grandfather clock is easy to recognize.

The ticking of a clock is regarded to be pleasant, perhaps even homely. The striking of a clock is also not regarded to be noise.

Information and ideas:
Recording to be identified by students or used for sound effects for a radio play/story.

Relevant for teaching:
Structure and function of a sensory organ
Senses discover the environment
Games to practise using the senses