I've been playing around with some Mosfets to control speed of a DC
motor.  I put the mosfet on a large chunk of aluminum to act as a heat
sink.  Then noticed that the drain of the mosfet is electrically connected
to the mounting portion of the mosfet.  The way I've got the circuit hooked
up its:

+V to Motor to mosfet drain then mosfet source to ground.

        This means the heatsink will have +12V on it.  Doesn't this cause a big
short when you're trying to mount the heatsink (usually meaning bolting it
to ground)?

        Just wondering if this is common and how to avoid it.  Could put something
between them, but that would ruin the thermal transfer to the heat sink.

Thanks,

Gary

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