30 | .01003 | .0002962 | 3376. | 1.879 |
| 31 | .008928 | .0002350 | 4255. | 2.371 |
| 32 | .007950 | .0001864 | 5366. | 2.990 |
| 33 | .007080 | .0001478 | 6766. | 3.771 |
| 34 | .006304 | .0001172 | 8532. | 4.756 |
| 35 | .005614 | .00009295 | 10758. | 5.997 |
| 36 | .005000 | .00007369 | 13569. | 7.560 |
| 37 | .004453 | .00005845 | 17108. | 9.532 |
| 38 | .003965 | .00004636 | 21569. | 12.02 |
| 39 | .003531 | .00003675 | 27209. | 15.16 |
| 40 | .003145 | .00002917 | 34282. | 19.11 |
+---------+----------+-----------------+----------------+---------------+

Inductive Neutrality. Where the resistance unit is required to be
strictly non-inductive, and is to be in the form of a coil, special
designs must be employed to give the desired inductive neutrality.

Provisions Against Heating. In cases where a considerable amount of
heat is to be generated in the resistance, due to the necessity of
carrying large currents, special precautions must be taken as to the
heat-resisting properties of the structure, and also as to the
provision of sufficient radiating surface or its equivalent to provide
for the dissipation of the heat generated.

Types. _Mica Card Unit._ One of the most common resistance coils
used in practice is shown in Fig. 117. This comprises a coil of fine,
bare German silver wire wound on a card of mica, the windings being so
spaced that the loops are not in contact with each other. The winding
is protected by two cards of mica and the whole is bound in place by
metal strips, to which the ends of the winding are attached. Binding
posts are provided on the extended portions of the terminals to assist
in mounting the resistance on a supporting frame, and the posts
terminate in soldering terminals by which the resistance is connected
into the circuit.

TABLE VII

30 Per Cent German Silver Wire

+---------+----------+-----------------+----------------+---------------+
| No. | | | | |
| B. & S. | DIAMETER | WEIGHT | LENGTH | RESISTANCE |
| GAUGE | INCHES | POUNDS PER FOOT | FEET PER POUND | OHMS PER FOOT |
+-------