As we start Pesachim in the study of Daf Yomi, we see that the Torah commands us to remove leavened bread, chametz, on Erev Pesach, in order to ensure that chametz will be neither seen nor found on our premises during the Yom Tov. The removal of chametz is achieved either by renouncing one’s ownership over it, bitul, or by physically destroying it, biyur. The rabbis established a procedure that combines both bitul and biyur.
Bitul chametz is performed on the evening of the 14th of Nissan. The ceremony commences with the searching for chametz, known as bedikat chametz. This is done by the head of the family by means of a candle that can reach dark recesses of the house. Before searching, the blessing Al Biyur Chametz is recited. After searching, the Kol Chamirah declaration is recited, the effect of which is to nullify any chametz one may have missed. During the fifth halachic hour, on the morning of the fourteenth of Nissan, biyur chametz is performed by burning all chametz in one’s possession that one does not intend to sell to a non-Jew, including the chametz recovered in the search the night before.
Because Pesach cleaning will likely have removed all chametz before bedikat chametz begins, the rabbis were concerned that the reciting of the blessing Al Biyur Chametz might be wasted if no chametz were found in the search. Therefore, some rabbis, including the Rema, recommend strategically placing ten pieces of chametz in various corners of the house before commencing the search. Others criticize this practice because one may forget where one placed them, or one may focus on retrieving them rather than looking for genuinely misplaced chametz. The practice has, however, survived the criticism and is generally accepted. If one forgets where one has placed a piece of chametz it is of no grave concern, since the recital of Kol Chamirah has a nullifying effect.
The Acharonim discuss whether a flashlight, instead of a candle flame, may be used for bedikat chametz. According to some authorities, a flashlight is prohibited because its broad light beam resembles a flaming torch, an avukah, which, like the Havdalah candle, was made of several parallel wicks. The Talmud in Pesachim expressly prohibits the use of the avukah for bedikat chametz. Furthermore, such authorities argue that the light from the bulb streaming through the glass of the flashlight is like the light streaming through a windowpane, which may not be used for bedikat chametz. Additionally, they contend that a flame is required for bedikat chametz and an electric or battery-produced light is not a flame.
Other halachic authorities, such as Rabbi Ovadia Yosef and the Shaarim Hametzuyonim Behalacha, quote authorities who permit the use of an electric light or a flashlight not only for bedikat chametz but also for the lighting of Shabbat candles. These authorities argue that an electric light and a flashlight do not resemble the avukah and that turning them on and off on Shabbat is biblically prohibited under the av melachah of kindling and extinguishing fire. That being so, such sources of light can also be used for the above described purposes, including bedikat chametz. Indeed, it is told that Rav Chaim Soloveitchik would make Havdalah with an electric light.