10 May
2010
10 May
'10
8:56 a.m.
At 04:51 PM 5/9/2010, Fred Cisin wrote:
I also see way too many students who were never handed
a bulb, a battery,
a nail, and some pieces of wire, . . .
My freshman son was recently assigned a task like this in science
class. They were to assemble a sort of circuit board by using
thin strips of aluminum foil, joined at corners, instead of wires,
taped to a piece of cardboard, and improvised switches with flaps
that could be pressed to touch the ends together.
The objective was to design a circuit that could show lamps
in series and in parallel, depending on which switches were closed.
The assignment paperwork said to use "Christmas bulbs". The power
supply was not specified, although it was hinted a 9-volt could be
pressed against contacts. I thought this was very unclear, as there
are several types of Christmas bulbs these days.
To simplify, I bought four $1 old-style incandescent 3 volt (two AA)
flashlights, disassembled the bulbs, soldered wires to them, and
inserted them into the circuit.
Anyone care to predict what happened with two of these bulbs in series,
either with 3 volts or 6 volts?
What happened when I tried LEDs, in series or parallel, with a
current-limited source?
- John