Fig. 84.
166. Current Detector. Fig. 84. To make a more substantial detector than [App. 110], the coil should be fastened to a wooden base. The coil may be made of 10 ft. No. 30 wire, as explained. ([§ 163].) A hole should be made in the base with a small awl or with a hot wire, and into this should be set a pin, head down. The hole need not be larger than the pin-head, and when you find out how high the pin-point should be above the base, the pin may be fastened in place with a little paraffine, which should be pressed into the hole around the pin. The coil may be fastened in place with paraffine. The ends of the coil may be connected with binding-posts, described in [App. 46], as shown, or with any other desired form.
The base should be 4 × 5 × ⅞ inches. The coil looks well when placed about 1 in. from the edge of the base. The binding-posts may be about 1 in. from the edges.
167. Current Detector. Fig. 85. This is more troublesome to make than [App. 111], but perhaps it looks more scientific.
Fig. 85.