| Fig. 139 shows how a current can be generated by two coils, H being connected to an astatic galvanoscope and E to a battery. |
| The coil of the galvanoscope, G V, has a magnetic field about it when the circuit is closed. |
| To test the voltage of batteries we must be able to control our galvanoscope. |
| To study the lines of force about a coil of wire like that upon the galvanoscope. |
| A galvanoscope is an instrument or apparatus, such as a magnetic needle, for detecting the presence and direction of electric currents, specially those of feeble intensity. |
| With two other wires connect the two copper plates with the galvanoscope binding-posts, and watch for any indication of current. |
