No. 62 978. 



Transformers. Inductive Repulsion. 



1009 



62978C. 1:5 



62 978 F. 1:5. 



629780. 1:5. 



62 078 H. 1:5. 



The experiments which can be carried out with the above collection of apparatus are essentially 

 the following: 



1 . Singing Membrane, Fig. A. The iron core is slipped down to its lowest point in the coil and the 

 iron membrane, with a space of approximately one millimetre, fastened above it. When the 

 magnet is excited the membrane gives a tone corresponding with the frequency of the alternating 

 current. 



2. Balance with Copper Disc, Fig. B. The balance is inserted on the apparatus holder in such manner 

 that the copper disc is 2 mm above this when the magnet is unexcited. When the current is closed 

 the copper disc is then repelled. 



3. Rotating Copper Disc, Fig. C. In the fork intended for the purpose is inserted the copper disc, 

 fitted with coloured sectors and with axis; the disc is held horizontally above the magnet while the 

 thick copper disc is inserted in such manner that one-half of the field is covered. 



4. Rotating Iron Disc with Copper Rim, Fig. D. This is inserted in the fork in place of the 

 previous disc; it is characterised by having two parts, a central iron part and an outer narrow 

 copper margin. In this experiment it is best to raise the iron core somewhat so that it is projecting 

 about 3 centimetres above the coil, and the iron prism is then set upon it. The fork is held in such 

 wise that the disc is perpendicular; moreover, as in the preceding experiment, the field is partially 

 covered by the stout copper disc. 



5. Rotating Ball, Fig. E. If one-half of the electromagnet is covered with the thick copper disc and 

 the wood ring, together with watch-glass and ball placed on the magnet, the ball is set rolling. 

 This experiment works particularly well if instead of the wood ring and watch-glass the glass vessel 

 is used and filled with enough water to allow the hollow ball to float. The rotation of the ball 

 is then extremely rapid and takes place about a horizontal axis. 



6. Spiral with Glow Lamp, Fig. F. Owing to the use of light material this device is so- constructed 

 that it can only just sink under water. If the device, together with the water-vessel, is placed 

 on the electromagnet and the latter excited, the lamp is rendered brightly incandescent. On the 

 other hand a repulsion occurs; the spiral with the glow lamp is raised up in the water and the 

 luminosity of the lamp appreciably decreases at the same time owing to the field becoming weaker. 

 This is a very striking experiment. 



It is also possible to show with this arrangement the damping effect of different materials. 

 If the copper plate is placed under the glass vessel the whole phenomenon almost disappears ; this 

 is also the case to a lesser degree when the iron plate is used, while the glass plate is without influence. 



7. Wood Frame with Ring, the latter suspended on fibres, Fig. G. The magnet core is lifted as far 

 as possible out of the magnetizing coil, the frame and ring slipped over the same and the latter 

 fastened to the carrier. Under the influence of the current the ring is raised up and is held sus- 

 pended by the fibres. 



Owing to eddy currents in the ring this becomes considerably heated in a very short time; 

 this heating also takes place to a corresponding extent in the other experiments. 



8. Broad Aluminium and Copper Ring. The copper ring remains suspended approximately in the 

 centre of the excited magnet core when placed above it, while the aluminium ring is entirely hurled 

 away. 



9. Ring with Pendulum Suspension. Fig. H. The apparatus is placed horizontally as shown in 

 Figure and the core pushed into the coil somewhat so that the oscillating ring can swing out. 

 The experiment is a variation of the preceding one. 



10. Hollow Copper Ring with Attachment Tube. Some water is poured into the vessel and the small 

 tube closed with a cork. The water, being heated by the eddy currents, evaporates; the cork is 

 driven out with a pop and a jet of steam issues from the small tube. 



1 1 . Mercury Trough. If this is filled with mercury and set upon the upright apparatus, the mercury 

 is set into a wavy motion by inductive influence. 



Cl. 2821,2823, 2824, 



2822, 2825. 2826, 2827. 



64 



