Bild

Siemens Stiftung

Eddy currents in metal objects

Graphic:
The principle of eddy current brakes.

If a metallic disc moves through a static magnetic field whose field lines are perpendicular to the direction of movement, voltages are induced in the disc and eddy currents form. According to Lenz's law, the induced current generates a magnetic field to oppose the change in magnetic field that produced the current.
The braking effect is examined at the edges of the static magnetic field. At the position where the disc enters the external magnetic field, the current tries to maintain the state "without the magnetic field?. Therefore, the current is directed such that its induced magnetic field offsets the external magnetic field. The fields oppose each other (in the graphic, the induced field is directed "outward?), resulting in magnetic repulsion. The resulting force counteracts the direction of movement, slowing down the disc.
The situation is reversed at the position where the disc exits the magnetic field. The induced current tries to maintain the state "with the magnetic field?. Therefore, it is directed such that its induced magnetic field strengthens the external magnetic field (in the graphic, the induced field is directed "inward?). This results in magnetic attraction. The resulting force once more counteracts the direction of movement, slowing down the disc again.

Information and ideas:
This principle is also applied to eddy current sorting of residual waste containing aluminum.

Medientypen

Bild

Lernalter

13-18

Schlüsselwörter

Electricity Magnetism

Sprachen

Englisch

Experiment

Siemens Stiftung

A5 Properties of solar cells (student instructions)

Experimentation instructions for Experimento | 10+:
Background information on the content and practical information on conducting the experiment "Properties of solar cells - Voltage, current and power". This experiment comprises six subexperiments.

The experiment comprises six subexperiments:
· First investigations with the solar cell
· Short-circuit current and no-load voltage at different distances from the lamp
· What happens when you connect solar cells in series or in parallel?
· Current and voltage with solar cells connected in series and in parallel
· How do solar cells connected in series or in parallel behave when shaded?
· Optimizing the power output of solar cells

For each subexperiment, the students are first provided with an overview of the materials to be used and safety information. This overview is followed by the detailed, step-by-step instructions for conducting the experiment. Afterwards, the students are asked to note their observations. Specific questions are used to guide the students as they analyze the results of the experiments. At the end, the students are asked probing questions related to the experiment (an answer sheet is available for teachers).

Notes:
· Observe the safety information in the instructions as well as the applicable safety guidelines for your school and discuss it with your students.
· This student instruction is also available in Word format (doc-file).

Anderer Ressourcentyp

Siemens Stiftung

Daniell cell as a redox system

Interactive graphic:
Simple diagram for building a Daniell cell.

In this graphic, the involved processes are only verbalized; electron flows and chemical equations are not shown.

The graphic can be labeled interactively, either individually or as a whole. Manual labeling on the interactive whiteboard is also possible.

Information and ideas:
In addition, there are further media related to the Daniell cell on the media portal of the Siemens Stiftung.

Anderer Ressourcentyp

Siemens Stiftung

Daniell cell (experiment setup)

Interactive graphic:
How is the Daniell cell built?


The experiment setup can be labeled interactively, either individually or in full. Manual labeling on the interactive whiteboard is also possible.

Arbeitsblatt

Siemens Stiftung

A5 How do solar cells connected in series or in parallel behave when shaded? (worksheet 5)

Worksheet for subject teaching in English:
For the student experimentation instructions of the same name. Methodology tool: picture sequence developed by Josef Leisen and Heinz Klippert.

Note: This worksheet has been developed especially for subject teaching in English and for language-sensitive subject teaching. It uses the picture sequence methodology tool developed by Josef Leisen and Heinz Klippert. The picture sequence is used to train students how to correctly comprehend and then explain the chronological and logical sequences of events.
Students whose native language is not English and who do not have strong English skills receive support and training in understanding the technical vocabulary. They work with the specialized vocabulary and in this way acquire the ability to communicate about specific subjects.


Dieses Material ist Teil einer Sammlung

Anderer Ressourcentyp

Siemens Stiftung

A5 Current and voltage with solar cells connected in series and in parallel (worksheet 4 answer sheet)

Answer sheet:
For the worksheet of the same name for subject teaching in English.

You can find more detailed information on the associated worksheet for subject teaching in English "A5 Current and voltage with solar cells connected in series and in parallel (worksheet 4),? which is available on the media portal of the Siemens Stiftung.


Dieses Material ist Teil einer Sammlung

Bild

Siemens Stiftung

Alkaline battery

Photo:
The alkaline battery is one of the most important electrochemical energy storage devices in everyday life. It is a galvanic cell consisting of a zinc anode, a manganese dioxide cathode, and potassium hydroxide solution as the electrolyte.


Information and ideas:
An example for the conversion of chemical energy into electrical energy.

Simulation

Siemens Stiftung

Photovoltaics - basic principle

Simulation:
Photovoltaics is the conversion of light into electrical energy. From the physics aspect it is an example of the important role that the quantization of energy also plays in the conversion of energy.

Light quanta impinging on a semiconductor generate conduction electrons at higher potential due to the internal photo effect. From there they can flow away via the external circuit and can be used. This effect is dependent on the energy of the photons and on the semiconductor material. An animation shows how the electric current flows in the photocell. Graphics explaining the internal photo effect in a semiconductor and the energy diagram of the solar cell can also be displayed.

Information and ideas:
Where are photocells used for producing electric power? What efficiency can be attained?

Übung

Siemens Stiftung

Internal resistance (cloze test)

Cloze test:
Voltage and current sources have resistance themselves, called internal resistance.

The properties of voltage and current sources with respect to their internal resistance are explained and the significance of internal resistance in series and parallel connections of batteries and solar cells is clarified.

Experiment

Siemens Stiftung

A5 Properties of solar cells (teacher instructions)

Experimentation instructions for Experimento | 10+:
Background information on the content and practical information on conducting the experiment "Properties of solar cells - Voltage, current and power". This experiment comprises six subexperiments.


If the subexperiments for investigating the electrical properties of solar cells are conducted in the suggested order, they form a learning unit that is very good for students to verify hands-on the basic knowledge of electricity they have previously learned. The fact that solar electricity is currently a hot topic will certainly help motivate the students. These experiments also provide an excellent opportunity to discuss the topics of renewable energy and energy transition, as long as the stu-dents have the relevant prior knowledge. The materials and apparatus supplied are sufficient to allow four groups of students to conduct the experiments simultaneously.

The experiment comprises six subexperiments:
· First investigations with the solar cell
· Short-circuit current and no-load voltage at different distances from the lamp
· What happens when you connect solar cells in series or in parallel?
· Current and voltage with solar cells connected in series and in parallel
· How do solar cells connected in series or in parallel behave when shaded?
· Optimizing the power output of solar cells

Notes:
· Observe the safety information in the instructions as well as the applicable safety guidelines for your school.
· All materials mentioned in the instructions will have to be purchased directly from commercial sources.