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16:25 IWF (Göttingen) English 1995

Crystallization of Evaporites in Saltworks

The saltworks of Secovlje (Portoroz, Slovenia) have been producing salt for 700 years. They can be used as a model for the study of microbiology and geochemistry of evaporite sequences of the geological past. The concentration of seawater and the crystallization of carbonates, gypsum and halite (NaCl) are documented and illustrated by graphics and microscope sequences. See films B 1839 and C 1906.
  • Published: 1995
  • Publisher: IWF (Göttingen)
  • Language: English
37:02 IWF (Göttingen) German 1997

Fachwerk als historisches Erbe - Stadtarchäologie und Denkmalpflege am Beispiel Göttingen

Unaffected by the war, Göttingen retains many well-preserved half-timbered buildings. The town in middle ages, methods of town archaeology and the principles of preservation are explained. Mistakes are illustrated in order to prevent their happening again in similar situations, for example in eastern Germany.
  • Published: 1997
  • Publisher: IWF (Göttingen)
  • Language: German
16:25 IWF (Göttingen) German 1995

Salzbildung in Meerwassersalinen

Seit dem 13. Jahrhundert wird in den Salinen von Secovlje (Portoroz) in Slowenien Salz gewonnen. Hier kann beispielhaft die Salzbildung bei der Eindunstung von Meerwasser studiert werden. Die geochemischen und mikrobiologischen Bedingungen in den Eindunstungsbecken sind vergleichbar mit Salzbildungen in der geologischen Vergangenheit. Die Konzentration des Meerwassers mit der Bildung von Carbonaten, Gips und Steinsalz wird dokumentiert und mit Graphiken und Mikroaufnahmen erläutert. Siehe auch Filme B 1839 und C 1906.
  • Published: 1995
  • Publisher: IWF (Göttingen)
  • Language: German
34:31 IWF (Göttingen) German 1996

Ende des Mansfelder Kupferschiefer-Bergbaus

After 850 years of mining the last large pit is closed. Aerial photos of the area, the pit and surroundings. Documentation of drilling, blasting, clearing, and walling of the dams constructed to hold the water back. History of copper slate mining in Mansfield with the various mining methods in animated sequences. Removal of surface installations and filling in the pit.
  • Published: 1996
  • Publisher: IWF (Göttingen)
  • Language: German
02:14 IWF (Göttingen) English 2003

Stabilization Using a Spinning Top

In an impressive demonstration, the precession effect is used to stabilize a very top-heavy device. A man tries to balance while sitting on a steel bar which can rotate freely around its horizontal axis. A top consisting of a lead-filled bicycle rim driven by an electric motor is attached to this bar with a joint allowing the top to be tilted away and towards the man, but not sideways. The center of mass of man and top are far above the bar. As long as the top is at rest, the man has to keep his feet on the floor to avoid tipping over. With the top spinning, pushing or pulling its axis will make the top precess, i.e. to move sideways. This motion can be used to balance the top-heavy system.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
02:03 IWF (Göttingen) English 2003

Angular Momentum as a Vector

A ventilator which can rotate freely around a vertical axis can be used to demonstrate that the angular momentum is a vector. A ventilator is mounted so that it can rotate freely around a vertical axis. It can also be tilted so that the air is blown either horizontally or upward. Upon turning on the ventilator, both the propeller and the driven air jet receive an angular momentum. Its vector points in the direction of the jet, parallel to the axis of the propeller. The ventilator receives an equal angular momentum in the opposite direction (opposite sense of rotation). The experiment is carried out for two different orientations of the ventilator.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
00:57 IWF (Göttingen) English 2003

Precession of a Spinning Wheel

A spinning top (gyroscope) does not follow a torque in the same way as, for example, a top at rest. Rather, it moves sideways, it "precesses". This startling behavior will be shown here. The top is a bicycle wheel with its rim filled with lead wire. It can be suspended on a rope dangling from the ceiling. The wheel is spun while holding its axle horizontal. Then, one end of the axle is attached to the rope. The weight of the wheel and the tension in the rope together cause a torque which, however, does not turn the axle into the vertical position, as would happen if the wheel were not spinning. Instead, the axle, which indicates the direction of the wheels angular momentum, circles on a horizontal plane around the point on which it is suspended. This sideways motion of a top under the influence of a torque is called "precession".
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
03:28 IWF (Göttingen) English 2004

Amperes Law

A long induction coil wound on a flexible hose is used to explore the magnetic field near current carrying conductors and also near a permanent magnet.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:33 IWF (Göttingen) English 2004

Induction motor

Eddy currents induced in an aluminum disk in a moving inhomogeneous field tend to move the disk along with the field. This is the principle of the induction motor.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:31 IWF (Göttingen) English 2004

Resolving power

It is shown that in an optical image the individual light spots are diffraction patterns caused by the opening of the imaging lens. The resulting limit of the angular resolution is demonstrated with the aid of two pairs of holes with different separations.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:41 IWF (Göttingen) English 2004

Eddy current brake

Forces are demonstrated which arise when an electric conductor moves through an inhomogeneous magnetic field.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:28 IWF (Göttingen) English 2004

Electromagnet

It will be shown that in a small electromagnet surprisingly large forces can be generated. However, these forces decrease drastically with the introduction of only a small gap between the pole faces.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:55 IWF (Göttingen) English 2004

Rotating magnetic field

A rotating magnetic field results from the superposition of two magnetic fields oriented perpendicularly to each other, which vary sinusoidally with equal frequency, but with a phase difference, ideally of 90 degrees.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:21 IWF (Göttingen) English 2004

Spherical aberration

The imaging error called "spherical aberration" is demonstrated by imaging a small coil of a light bulb.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:03 IWF (Göttingen) English 2004

Paramagnetic matter

Paramagnetic matter gets pulled into regions of a large magnetic field. For the demonstration, liquid oxygen is poured into a shallow container placed in front of an electromagnet with non-parallel faces.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:58 IWF (Göttingen) English 2004

Astigmatism

The imaging error called astigmatism occurs when light travels not parallel to the axis of the lens, but under an angle. Instead of image points, extended lines or streaks are formed.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:48 IWF (Göttingen) English 2004

Cone of reflected light

The reflection of light is demonstrated using a polished steel tube. The reflected light has the shape of a cone.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
00:47 IWF (Göttingen) English 2004

Perspective

Two-dimensional images of three-dimensional structures have a perspective, that is a certain ratio of size and distance for things which lie behind each other. The perspective depends on the position of the centers of the projection, which in imaging lie in the centers of the entrance- and exit-pupils. Using the images of two objects positioned at different distances from the imaging lens, the perspective and its changes will be shown.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:21 IWF (Göttingen) English 2003

Dynamic Stability of a Bicycle Chain

Belts made of soft material which are flexible while at rest, in this case a chain made of metal links, can become quite rigid, independent of their shape, when their tangential velocity is sufficiently large. This phenomenon is called "dynamic stability". Through the radial forces the chain stiffens, and after it gets thrown off the toothed wheel, it roles along the floor, jumps over a wooden beam, and collapses into its shapeless form only after coming to rest on the rug after colliding with the wall. It is clearly seen how the stiff chain deforms somewhat as it hits the beam. Note also how long the chain continues to rotate on the rug near the end of the experiment, before it finally comes to rest and collapses.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
01:16 IWF (Göttingen) English 2004

Bent light ray

A trough contains a sugar solution with a vertical concentration gradient, so that its index of refraction decreases with increasing height. A laser light beam enters the trough, tilted slightly against the horizontal direction. As it moves through the liquid, it is bent, as can be observed through scattering.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:42 IWF (Göttingen) English 2003

Conservation of Angular Momentum Using a Rotating Chair

Conservation of angular momentum around the vertical axis of a rotating chair. A man sitting on a rotating chair with very little friction uses weights, a spinning wheel, and a wooden hammer with a long handle to demonstrate the vector nature of the angular momentum as well as its conservation in the absence of external torques. This setup allows to limit the observation to a single (the vertical) component of the angular momentum.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
01:04 IWF (Göttingen) English 2003

Action = Reaction

A demonstration that forces between two bodies always occur in pairs: They are opposite in direction and equal in magnitude. These facts were summarized by Newton with the statement "action = reaction". Two people are standing on flat carts on a level floor, a few meters apart. The forces are exerted by means of a rope. The experiment shows that in both cases the forces are equal in magnitude and opposite in direction, in short: action = reaction. It also shows that the total momentum of the system is conserved.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
01:45 IWF (Göttingen) English 2004

Chromatic aberration

Chromatic aberration occurs in imaging as result of the wavelength dependence of the index of refraction. It will be demonstrated on a special example.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:46 IWF (Göttingen) English 2004

Polarized light

The plane of polarization of a light beam which has been polarized by passing it through a Nicol prism is made visible through scattering in a slightly milky liquid.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
00:40 IWF (Göttingen) English 2003

Elastic Collision in Slow Motion

Elastic collision between two bodies in slow motion through the proper choice of the experimental conditions. It will be shown that during the collision the kinetic energy is briefly converted into potential energy and then back into kinetic energy. The slow collision, achieved through the proper choice of masses and spring constants, demonstrates clearly the transformation from kinetic to potential energy, and back again, as is characteristic for elastic collisions. This experiment also demonstrates the conservation of linear momentum.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
00:45 IWF (Göttingen) English 2003

Conservation of Linear Momentum

According to the law of the conservation of momentum, which states that in every closed system the sum of the individual momenta stays constant. They can be exchanged inside the system. Three examples will be shown. In all three cases, the total momentum of the closed system remains constant.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
06:27 IWF (Göttingen) English 2004

Experiments with Water Waves

Some of the fundamental properties of waves are demonstrated using surface waves in a water trough.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:21 IWF (Göttingen) English 2003

Measurement of the Electric Field of the Earth

The electric field of the earth will be determined. A parallel plate capacitor of area 1 m2 is attached to the end of a long bamboo pole. The capacitor is connected to a ballistic galvanometer calibrated to measure current pulses (charges). On a balcony outside the lecture hall, the capacitor is held with its plates horizontal.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
01:27 IWF (Göttingen) English 2004

Model of a Travelling Wave

The connection between circular motion, phase difference and wave propagation is shown with the help of a series of beads arranged to form a right-handed helix.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
03:04 IWF (Göttingen) English 2004

Induction in conductors at rest

A changing magnetic field generates an electric field.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
03:10 IWF (Göttingen) English 2004

Induction in conductors in motion

A conductor moving in a magnetic field experiences an electric field.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
07:36 IWF (Göttingen) English 2004

Model Experiments for Streamlines

The goal is the demonstration of two-dimensional streamline patterns as they occur when non-viscous fluids flow around obstacles. The patterns shown are models, since they have been produced in a viscous fluid under conditions of laminar flow.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
02:09 IWF (Göttingen) English 2004

Capacitance of a sphere

Experimental determination of the capacitance of a sphere.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:22 IWF (Göttingen) English 2003

Circular Oscillations

Through superposition of the linear oscillations of two leaf springs of almost equal frequencies, linear, elliptic and circular oscillations can be generated and shown by optical projection.
  • Published: 2003
  • Publisher: IWF (Göttingen)
  • Language: English
01:27 IWF (Göttingen) English 2004

Electric wind

At sharp corners, even small voltages can lead to large electric fields. They can ionize the surrounding air, making it electrically conducting.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
01:22 IWF (Göttingen) English 2004

Soap bubbles in an electric field

The repulsive force between two bodies carrying charges of the same sign will be demonstrated.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: English
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