Italian physiologist Luigi Galvani (1737-1798) is noted for his studies on the effects of electricity on animal nerves and muscles. Galvani accidentally discovered that the leg of a frog twitched when touched with an electrically charged scalpel.
Principles discovered by Galvani and Oersted led to Volta’s invention of the first electric battery. In this experiment you’ll build a Galvanometer. A Galvanometer is an instrument for detecting the strength and direction of electrical current. Materials you will need:
- Energizer® Power Pack
- Floating needle from Oersted's Experiment
- Varied large lengths of number 22 insulated copper bell wires with approximately 1" of insulation stripped from all ends
- Switch or alternate commercial knife blade switch
- 3V Bulb and bulb holder
- 1. Wrap wire around the floating needle dish five times. Set up the floating needle as in Orested’s Experiment. Connect one wire end to the switch and the other wire end to the negative lead of the Energizer Power Pack. Connect another wire from the switch to the positive lead of the Energizer® Power Pack.
- 2. Observe where the needle is with the switch open then close the switch and observe how far and fast the needle turns.
- 3. Increase the wire turns around the dish five more times. Repeat step two. Did the needle turn farther and faster?
- 4. Replace the floating needle with a compass and connect the bulb holder to the circuit between the compass and the switch.
- 5. Repeat steps 2 and 3 with the compass in the circuit instead of the needle. Note the changes, if any.
Performing the above experiments show that the magnetic field generated in an electric circuit can be changed. A Galvanometer works on some of the same principles. As the current flowing through a Galvanometer increases so does the magnetic field which in turn further deflects the needle.