Ans. Exposed wiring is cheap and accessible; a short circuit or ground is easily located and repaired. Concealed wiring, especially when placed under the floor, has the advantage of being out of the way, and thus protected from injury.
Ques. In wiring a dynamo what are the considerations with respect to size of wire?
Ans. All conductors, including those connecting the machine with the switchboard, as well as the bus bars on the latter, should be of ample size to be free from overheating and excessive loss of voltage. The drop between the generator and switchboard should not exceed one-half per cent. at full load, because it interferes with proper regulation and adds to the less easily avoided drop on the distribution system.
CHAPTER XXV
AUXILIARY APPARATUS
There are numerous devices that must be used in connection with dynamos and motors for proper control and safe operation. Among these may be mentioned:
1. Switches;
2. Fuses;
3. Circuit breakers;
4. Rheostats;
5. Switchboards.
Switches.—A switch is a device by means of which an electric circuit may be opened or closed. There are numerous types of switch; they may be either single or multi-pole, single or double-throw and either of the "snap" or knife form.
Ques. What is the difference between a single and double-pole switch?
Ans. A single-pole switch controls only one of the wires of the circuit, while a double-pole switch controls both.