[Avodah] Sparks and motors

[D&E-H Bannett]

R' Micha asked for my comment on his statement:
 <<I think that for many motors, the sparks are pesiq 
reishei. For most cheap motors, unless they get their RPM 
rate off the voltage cycle of the AC line, they have brushes 
and therefore spark quite frequently.>>

How can I refuse R' Micha?   So:
The cheapest motor to manufacture is the a-c induction 
motor. It does not have brushes or rotor coils. It is, 
therefore, the motor used whenever possible, a large 
majority of motors.  Only when continuous variation of motor 
speed is required is a brush motor used.  Of late, using 
feedback and modern electronics, it is possible to get 
continuous control of speed from induction motors. This is 
making brush motors even less common.

Of course with mechanical contacts there are usually sparks 
at the moment that a motor is disconnected and to a lesser 
extent when connected. By modern electronic methods, 
connection and disconnection can be made without sparks.

RSZA makes a strong case for the sparks being p'sik reisha 
d'lo nicha lei d'rabbanan and eino mitkaven, kil'achar yad, 
and u'mkalkel and, therefore, mutar.
R" L.Y. Halperin makes a weaker case, but in my 35 years of 
working with him, he never assered any device because of 
unavoidable sparks.

Something that is usually not considered by the poskim is 
that the electric spark is a completely different phenomenon 
from the spark mentioned in historic halakha. The "halakhic" 
spark is the oxidation or destruction of material. The 
electric spark is the result of the movement of quantities 
of electrons through the air.  Both cause light. Can one 
learn the halakhic category of the electric spark, assur or 
mutar, from comparison with the other phenomenon?


k"t,

David 

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