Available online
Description
The first tv programme of this course is strongly linked to the unit section on charges in motion. Demonstrations of water flow in glass tubes and mechanically agitated polystyrene balls provide us...eful analogies for electric current in a wire and thermionic emission of electrons from a heated filament respectively.
The first tv programme of this course is strongly linked to the unit section on charges in motion. Demonstrations of water flow in glass tubes and mechanically agitated polystyrene balls provide us...eful analogies for electric current in a wire and thermionic emission of electrons from a heated filament respectively.
| Module code and title: | TS282, Electromagnetics and electronics |
|---|---|
| Item code: | TS282; 01 |
| First transmission date: | 22-01-1972 |
| Published: | 1972 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:03 |
| + Show more... | |
| Producer: | Tony Jolly |
| Contributors: | Peter Chapman; John Sparkes |
| Publisher: | BBC Open University |
| Keyword(s): | Charges in motion; Current; Electron beam; Model analogies; Oscilloscope trace; Thermionic emission; TV picture; Voltage waveform |
| Footage description: | John Sparkes introduces the programme. He explains why it is useful to have models when studying electron flow. Peter Chapman with a water flow model. The model is a hydraulic analogy of current flow - Current = flow of charge. Chapman points out the components of the model and then operates it. Results are sumarised by an equation. John Sparkes explains why steady force induces a steady velocity in both the water flow model and in an electric circuit. Chapman with a model which analogues a current in a copper conductor. The electrons are modelled by small balls. Chapman uses the model as an aid in explaining why electrical forces are kept inside the conductor. Chapman uses the same model to show how thermionic emissions take place. J. Sparkes with a simplified diagram of a cathode ray tube. He points out the components and explains the function of each. Chapman with an analogue of a cathode ray tube. He rolls small balls down a soft membrane. The potential of the focusing electrodes in the cathode ray tube are simulated by gravitational hills. Sparkes uses the cathode ray tube diagram again to explain why extra deflection is needed to move electron focus on a screen. He explains how this is done. Chapman with cathode ray tube simulator, the deflection electrode is simulated by a gravitational hill. Sparkes uses a 3 dimensional model of an electron deflection plate to explain how controlled deflection is achieved. Shot of oscilloscope screen with time base dot moving across the screen shows the result of electron deflection. Chapman explains how deflection is controlled in the oscilloscope. Chapman with the working parts of a cathode ray tube. He points out each component in turn. Chapman now holds up a television picture tube. He compares this with the cathode ray tube pointing out similarities and differences. Sparkes explains how electron scanning creates a picture on a television screen. Chapman simulates a television raster on the oscilloscope screen. Sparkes explains how the intensity of focused electron spots on a television screen can be varied. He uses the Open University symbol to show why intensity is important for T.V. pictures. Shot of voltage applied to the grid of T.V. screen showing voltage variations of all 625 lines. |
| Master spool number: | 6LT/70374 |
| Production number: | 00521_2105 |
| Videofinder number: | 696 |
| Available to public: | no |
