Question:

Why can't I use electrical appliances on Shabbos?

Discussion:

It is common knowledge that the use of electrical appliances is prohibited on Shabbos however, the reason for the prohibition is not so clear. We will put forth some of the reasons for the prohibition.

Molid - Creating a new entity:

One reason given by the poskim for the prohibition of using electrical appliances is the concept of Molid (creating something new). By allowing an electrical current to run through an appliance you are effectively creating a (new) usable appliance, which is prohibited on Shabbos. This is the opinion of the Bais Yitzchak (2:31). In a similar vein, Rav S.Z. Auerbach writes that the prohibition is the creation of sparks, which are generated by the electrical current (Minchas Shlomo 1:10:7).

Makeh B'Patish - Finishing touch:

The opinion of the Tzitz Eliezer (6:6) and the Minchas Yitzchak  (3:41) is that when an electric current is introduced in the appliance you are effectively putting the finishing touch on an object that until now was not complete since it did not have a use.

Boneh - Building:

The Chazon Ish (Shabbos 50:9) was of the opinion that when a circuit is completed it is a form of the Av Melacha of Boneh.

Bishul - Cooking:

An additional reason given by the Chazon Ish for this prohibition is when the current passes through the wire it causes the temperature of the wire to rise above Yad Soledes Bo (110 degrees F). This is under the melacha of Bishul.

Summary:

It is accepted that the use of electrical appliances is prohibited on Shabbos although the reason is a cause of considerable debate. One outgrowth of this debate is the possible permissibility of having a non-Jew turn on or off an appliance. A rav should be consulted if the need for this arises.