Get a small compass and show how it is related to the foregoing experiments. Emphasize its use to mariners. If possible, get a piece of lodestone and show its magnetic properties.
ELECTRICITY
Half fill a tumbler with water and add about a teaspoonful of sulphuric acid. Set in this a piece of copper and a piece of zinc, but do not let them touch. Make a coil by winding insulated wire around a block of wood about ten times. Remove the wood and place a compass in the centre of the coil. Join the ends of the wire to the two metals in the tumbler. The sudden movement of the needle will be taken as the indication of a current.
Let pupils try experiments with many pairs of solids, such as lead and silver, carbon and glass, wood and iron, tin and zinc, and liquids such as vinegar and brine.
Show pupils how to make a simple battery. See home-made apparatus, page 50, and consult Laboratory Exercises by Newman. Two or three dry cells will be found sufficient for any experiments, but the home-made battery is to be preferred.
Show pupils how to make a magnet by winding a piece of insulated wire around a nail and joining the ends of the wire to the battery. Make a horse-shoe magnet by bending the nail and winding the wire about both ends in opposite directions.
As an application of the electro-magnet, show pupils how to make a telegraph sounder. (See Manual on Manual Training.) If possible, examine the construction of an electric bell. The motor and electric light are other common applications of the current. Take up the uses of the motor in factories, and for running street-cars and automobiles. Show the necessity for a water-wheel or engine to produce the current, and for wires to connect. Explain that batteries are not used to produce large currents, but that machines called dynamos, similar to motors, when driven by steam or water-power, will yield electric currents as batteries do.
STEAM
The power of steam may be shown by loosely corking a flask and boiling the water in it until the cork is driven out, or by stopping the spout of a boiling tea-kettle, or by letting a stream of steam impinge on a toy paper wheel. Encourage pupils to learn all they can about steam and gasolene engines and their uses.