Fig. 25
You call at some apartment house where there is no hall boy, but a row of push buttons labelled with the names of the tenants. You push a button and the door which was locked opens apparently of its own accord. To say that the door opens by electricity is only to add mystery. What does happen is that an electric bell up in the apartment rings in response to your push of the button, and in reply the tenant pushes a button and the door is unlatched by an electro-magnet concealed in the door casing ([Fig. 25]).
So I would say that the first key to the Electric Show or to the multitude of electrical appliances which you meet in life is the electro-magnet. Consider the motor as one illustration of its use.
If you are really to understand the Electric Show you should go twice. I advise going with this key alone first and note down all the applications of electro-magnets which you can find there. When you have done so I shall be glad to have your report.
VI
APPLICATIONS OF THE ELECTRO-MAGNET
It became quite the rage now among the boys to find as many uses of electro-magnets as possible. These were reported and explained to the club and a list kept. This list included:
- 1. Dynamo.
- 2. Magneto.
- 3. Ammeter.
- 4. Wattmeter.
- 5. Motor.
- 6. Electric piano and organ players.
- 7. Electric door openers.