. The Pharmaceutical era. revolve in a magnetic-field, and the development of electric energy is propor-tional to the mechanical energy required to revolve thearmature against the resistance offered by the lines offorce. The dynamo, then, is simply a device for the con-version of mechanical into electrical energy. This proc-ess can also be reversed, for if a current generated byone dynamo is passed in through the brushes of another,the armature of the latter will be caused to revolve, butin a direction opposite to the armature of the machinefrom which the current comes. It is customary, there-
. The Pharmaceutical era. revolve in a magnetic-field, and the development of electric energy is propor-tional to the mechanical energy required to revolve thearmature against the resistance offered by the lines offorce. The dynamo, then, is simply a device for the con-version of mechanical into electrical energy. This proc-ess can also be reversed, for if a current generated byone dynamo is passed in through the brushes of another,the armature of the latter will be caused to revolve, butin a direction opposite to the armature of the machinefrom which the current comes. It is customary, there-fore, to say that a miitor is simply a dynamo reversed,though owing to the different purpose which they are in-tended to serve there is usually more or less variation inthe details of the two machines. By attaching a pulleyto the spindle of the armature the rotation of the latter-can be communicated to machinery through belting. KIg. 104 -Diagram of Dynamo ^ViDrum Armature. the field may eithera galvanic battery or bean-. Modern Dynamo. other , or a portion of it.* own current may becaused to pass around the poles. In the last case thepoles must retain a little residual magnetism in order tostart the current when the armature is set in motion. Permanent magnets cannot be made sufBeiently power-ful for large machines, and are only employed wherestrong currents are not required. Alternating and Direct Current. The Commutator.— As the di-rection of the current in a conductor depends upon whichpole of a magnet it fronts, it follows that the current Inany portion of the armature will bo reversed as it passesfrom one pole to the other, and will pass out throughthe brushes first in one direction and then the currents are known as alternatinii cvrrents. If a direct current is wante<], or a current in one direc-tion only, a device called a cnmmiitator is made use simple form of this is a divided brass ring covering theend of the armature spindle, and connecti
Size: 1564px × 1598px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectdrugs, booksubjectpharmacy, bookyear1
