Author Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt:... to any one of a series of thermal-junction pairs, or to the standard cell circuit. The circuit has a great many features in common with that of the earlier apparatus previously described in detail,2 and these need not be considered again at this point. Some differences, however, will be noted. The galvanometer sensitiveness is independent of the position of the contact P since moving this contact in no way affects the resistance of the galvanometer circuit. The sensitiveness being constant, a resistance W has been inserted in the galvanometer circuit, and by this means the sensitiveness adjusted until the deflection reads directly in hundredths of a degree. No special provision is made for reversing B and N, as experience with the earlier apparatus showed this to be unnecessary. The new apparatus differs from the old, also, in that the thermometer must be detachable. Two heavy wires have therefore been run to two metal blocks in each calorimeter, and to these the thermometer can easily be attached. It will be noted in fig. 7 that each calorimeter is not provided with an entirely independent set of connections, but that the chair calorimeter and calorimeter No. 4 are connected in parallel, as are also calorimeters Nos. 3 and 5. This is allowable because other considerations prevent the calorimeters thus joined from ever being used at the same time. Fig. 6. Elementary wiring diagram of modified apparatus. Current from the battery B flows through PI), this being part of the slide wire CD, then through the resistance H and finally returns to the battery through the ammeter A. The thermal junction system TT is connected through the galvanometer G to the points C and D, this circuit being free from sliding contact. iIt will be seen that the method as described i...