On 14 Feb 2007 09:32:25 -0800, "Bob" wrote:

On Feb 14, 11:04 am, "HK" wrote:
Thanks everyone. Good information here.

This is a Grade 6 project and I was a little distressed to find that even
the basic concepts of electricity haven't been taught yet they are supposed
to build a basic circuit and working model.

For instance, my daughter assumed that to power two 6v lights, she needed a
12v power supply. Yikes.

Nothing wrong with that as long as they are in series.


Is Grade 6 too early to teach Ohm's Law? Should they be learning to hook up
basic circuits without learning Ohm's Law and the concepts of voltage,
current and resistance?

No. a good mix of math and science.



Some of this stuff is coming back to me. Am I correct in assuming that the
problem with wiring the lights in series is there is too much cumulative
resistance at the far end of the circuit to light the lights?

Go back to Ohms law. 2X resistance = 1/2 current


2x resistance * 2x voltage = 1/1 current (as in 2 6V bulbs in series
on 12V).


FYI, we're building a small airboat. There are four 3v LED lights powered
by 2 "C" batteries and a single 6v motor powered by 4 "C" batteries.

Aahhh... Remember that we've been talking incandescent light bulbs.
A LED is a diode and not a bulb even though it gives off light.
Although the same principles apply since LED's use a dropping resistor
to limit current, similar to items in parallel.


LEDs can be connected in series as long as the voltage is high enough.
Then, only one resistor is needed.



Any suggestions on a fun followup project that will help both of us learn
more electricity concepts?

Google or your local library.
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy