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Station 4: Data acquisition & Power supplies

Generation of an alternating voltage, rectification and smoothing


An alternating voltage is induced in a coil in the (alternating) field of a periodically moving magnet. The characteristic of a diode to allow electric current only to pass in one direction is used to rectify the induced alternating voltage. A capacitor that is connected in parallel to the load (resistance) smoothes the rectified alternating voltage.

We investigate our heartbeat – electrocardiography


The heart is a hollow, muscular organ that comprises several secondary muscles. These secondary muscles contract and relax successively, thus pumping the blood through the heart. These muscle activities can be measured electrically as a whole at the surface of the skin with the aid of a so-called electrocardiogram (ECG). The same pattern repeats from heartbeat to heartbeat. A heartbeat is the regular sequence of electric excitations (action potentials). You can discern (record) the different partial activities of the cardiac muscle that follow each other with an electrocardiogram. This is why the ECG is also referred to as a „heart curve“. A doctor can identify various cardiac disorders by looking at the specific ECG pattern of the heart that is recorded with an ECG machine which is licensed for diagnostic purposes.

Force reduction with a two-sided lever


The students will observe the relationship between weight and the length of the lever arm of a two-sided lever. They will notice that the point of application of different masses affects the effort which is necessary in order to keep the lever in balance. In addition, they will see how the force, which needs to be applied, changes depending on the point of application of the spring balance or force sensor. They will conclude that force (or effort) can be reduced with the aid of a two-sided lever if the mass and spring balance or force sensor are positioned in a suitable manner.

Characteristic curves of semiconductors with Cobra4


The current-voltage characteristic of a semiconducting diode is measured.
The collector current in dependency on the emitter-collector voltage is measured for different values of base current strength through a NPN transistor.

We examine our drinking water with Cobra4


This experiment shows how much the quality of drinking water of various locations in the same region can vary. The comparison of tap water with bottled mineral water and distilled water leads to surprising results.

What kind of measurements are performed to determine the weather conditions and to make a weather forecast?


We perceive weather when it changes apruptly. In such situations, changes in air temperature, air pressure, humidity and light intensity can also be determined without measurement instruments. Normal weather changes as they happen every day, can best be determined with a weather measurement instrument.

Why don’t I sink in salt water?


Everyone knows by observation that a stone sinks in water while a piece of wood keeps floating. Why does a heavy ship or a pontoon made of concrete swim? Think of taking a bath in the Dead Sea…
What may be the reason why the immersion depths of objects as well as humans in salt water and sweet water is different?

Why am I cold when I am wet


Summertime – time to take a dip in fresh water. The sun is shining, and swimming pool and sea lure us. To cool down, we immerse ourselves in water, however, after we have left it again, we feel colder all of a sudden. Sometimes we prefer to stay in the water because outside it feels so cold. Why is that so?

Do the flames of lighters or candles have different temperature zones?


As a child we have proven our courage by moving our fingers through the flame of a lighter or a candle. Maybe we noticed that it is easier to get burnt in a lighter flame than in a candle flame? Why is that so?