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185
Diagram of Connections.
The above cvtt represents the way to connect the Arc Lamp, Resistance, etc., to the main supply of electricity in the Hall. The positive wire or lead is connected to the upper carbon of the lamp, and the negative to the lower. A Resistance must he inserted in the circuit to check the flow of the current, which would otherwise be too great. One of the leads to the lamp is therefore broken, and the two loose ends inserted in the two terminals of the Resistance. An ammeter should be similarly inserted to measure the quantity of current passing through the lamp. Less Resistance gives more current and brighter light Higher voltages (of the supply main) require more resistence. The positive (plus upper) carbon burns away at twice the rate of the negative (minus), and should therefore be considerably thicker, and it should be cored to keep the light steady. In the case of alternating current, both leads are alike and may be connected up indiscriminately, and the carbons should be of equal size and both cored.
SPECIAL AMMETER
SMALL SIZE CENTRAL STATION TYPE.
For showing at a glance the current in amperes passing through the lamp at any moment. This instrument shows in an instant whether the lamp requires "feeding," and is in various ways a great boon to the operator' It is beautifully made, and is absolutely accurate. 5-inch dial. Any desired reading may be had. The following scales are kept in stock :
Main
PRICE.
10 to 20 AMPERES 10 to 50 20 to 100
4 O
6 0
7 6
NOTE. Ammeters must be connected in series, so that the main current passes through the ammeter on its way to the lamp (see diagram). Our special instruments differ from others in being equally adapted tor either alternating or continuous current.
FLEXIBLE WIRE.
Cotton and Indiarubber Covered, to carry up to 30 amperes.
Price, per Yard, 2s.