Halakhah do Beca 4:10

The Mishnah (Beitzah 4:7) teaches the well-known rule that although one may transfer fire on Yom Tov, it is forbidden to create a new fire on Yom Tov. The poskim debate whether this constitutes a biblical or rabbinic prohibition (see Bei’ur Halachah 502:1 s.v. Ein Motzi’in). When incandescent bulbs first were introduced, a few prominent poskim permitted lighting an incandescent bulb on Yom Tov, arguing that lighting an incandescent bulb constitutes a transfer of fire rather than starting a fire (see Encyclopedia Talmudit 18:178). This approach, however, is rejected by the overwhelming majority of authorities primarily because it emerges from a mistaken understanding of how an incandescent bulb works. Those who permitted this lighting thought that the flow of electrons in the filament is what causes the bulb to glow. They believed that when one completes a circuit, the electrons in the filament then have a path in which to flow and thereby cause the filament to glow. According to this understanding, when one turns on a light, he simply is transferring the electrons. Rav Shlomo Zalman Auerbach (Teshuvot Minchat Shlomo 1:9 n. 5), however, notes that this is an erroneous understanding of how an incandescent bulb operates. The glow does not result from the flow of electrons but rather from the resistance in the wire to the flow of the electrons in the filament. Thus, one clearly creates fire when turning on an incandescent bulb, and as such, doing so is forbidden on Yom Tov. The accepted opinion is that of Rav Shlomo Zalman.⁷⁸Rav Shlomo Zalman Auerbach develops this point at great length in his seminal work on electricity known as Me’orei Eish (ch. 1-3) Among the many authorities who concurred that turning on an incandescent light is forbidden on Yom Tov are Chazon Ish (ad. loc.), Rav Yaakov Breisch (Teshuvot Chelkat Yaakov 1:51), Rav David Zvi Hoffman (Teshuvot Melamed Leho’il ad. loc.), and Rav Ovadia Yosef (Teshuvot Yabia Omer O.C. 1:19).

Both Rav David Zvi Hoffman and the Chazon Ish note that it is prohibited to complete circuits due to the sparks that are created in the process. They argue that the sparks generated when completing an electric circuit fall under the rabbinic prohibition to create sparks from wood or stones (Beitzah 4:7).