What is the problem with shaking one of the no battery/shaking flashlights which is on on shabbos?

  • 2
    Do you mean that the flashlight is already on from before Shabbos, and you want to shake it to make it stay on for longer?
    – Alex
    Feb 4, 2010 at 18:48

1 Answer 1


Any reason this isn't analogous to winding up a mechanical watch that's currently ticking (on-time)?

The watch case was discussed by R' Shlomo Zalman Auerbach IIRC; it was considered "fixing" the watch and prohibited. Heard in Rabbi Heinemann's discussion of Sabbath-mode ovens.

  • 2
    If anything, I would expect this case to be more severe, since you're generating electric charge, and for whatever reason, we hold using electricity to be prohibited. In fact, if it's an incandescent light, charging it could be considered within the rubric of adding fuel to a fire.
    – Isaac Moses
    Feb 4, 2010 at 18:57
  • Let's assume the bulb is an LED, or else as you say, end discussion. I figured the watch case is well-established by now, so our flashlight is certainly no BETTER than that. Makes for a quick way to prohibit it.
    – Shalom
    Feb 4, 2010 at 19:16
  • One reason given for the electricity prohibition is "fixing" a broken circuit by flipping the switch; that wouldn't apply here as you're leaving the switch in the "on" position. But other reasons -- such as "fixing" a device that would otherwise soon become unusable (as in the watch), or generating, might. While R' Shlomo Zalman wasn't convinced that merely flipping a switch violated the prohibition of "molid" by creating something new (see yutorah.org/lectures/lecture.cfm/722406/Rabbi_Josh_Flug/…), you could reason that generating might.
    – Shalom
    Feb 4, 2010 at 19:19

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