These were told to me by a friend who once attended Devry Inst.

These were told to me by a friend who once attended Devry Inst. in
Arizona (a tech. school for electronics types). Three favorite
practical jokes were:

(1) The access to the supply room (to obtain lab materials) was via
a Dutch door (two-piece job where either top or bottom could be
opened independently), where the top half was left open so
students could lean over and request supplies. The lab grunts
wired a thin filament wire to a power supply and strung it across
the top of the bottom portion of the door. Normal instincts of
students led them to lean or place hands there while waiting for
materials, and were met with a small yet satisfying jolt.

(2) This one I've heard of from various sources. Charge up a bell-type
capacitor and tape the leads in such a way that they are almost
but not quite touching. Call to the victim with a rousing "Here,
catch!" and lob the cap to them. When they catch, the slight
squeezing pressure will connect the leads and the capacitor will
pop. (VARIATION: Leave 'loaded' cap on chair for them to sit on)

(3) The most common labs involved circuit design and troubleshooting,
and students were forever wary as they applied power to a new circuit
for the first time. My friend's prank involved running some thin
hollow plastic flex tubing from his lab station to a point below and
behind the victim's station. He would then light up a cigarette and
wait. As soon as the victim applied power to his circuit, he would
blow ciggie smoke into his end of the tube. Within a few seconds,
victim would see smoke rising from his board and cut power. He would
examine board, find no trouble, and fire it up again. Soon smoke
would appear ... this can be stretched out for a good long time, or
until he sees the tubing.