Forum

[PeteF]

Blimey, now I'm confused.
"21W bulb about 6ohm each, two in parallel 3ohm"
I'm no electronics expert (or even inexpert) but how can two bulbs in parallel half the resistance?

[papasmurf]

Pete F Explanation here:-

http://www.tpub.com/neets/book1/chapter3/1-26.htm

[jefrs]

Thanks Papasmurf. Nice example.

I'm not trying to blind you with science, I'm desperately trying to keep it simple.

Problem is what I think is simple schoolboy stuff turns out not. I often pointed out to them that if my lab techs couldn't understand my procedures, it was my fault not theirs, and the worst one for that had an MSc (go figure).

[PeteF]

OK, I understand that now.
If I think about it in my usual way with electrics (water in hose, flow, size of hose etc) I can see that the electrons have two "ways through" in the parallel circuit so half can go through each way which halves the "difficulty". If they suddenly have only one "way through" its now twice as "difficult" In other words, two nozzles can pass a given amount of water twice as easily as one.
I know that's completely unscientific but it helps me understand what's going on even if nobody else does.
A day without learning.........

[Scalyback]

I spent many years working for electrical companies, knew all the formulae, but in the end when it didn't work, I just used to equate the circuit with water, pipes, valves and tanks, and that pretty much got me the answer!

[Beezabryan]

Never mind about all the scientific, pseudo or otherwise, bullshit
The guy asked a question without telling the whole story.
he now tells us that the flasher unit supplied by Hitchocks as part of a kit failed and as a stopgap fitted a car unit of unknown parentage.
May I humbly suggest that he speak to Hitchcocks, get the correct flasher unit fitted.

[PeteF]

Oh come on Bryan, I admit the thread did get derailed a bit but it's interesting stuff. Hardy bullshit.

[Dennis C]

OK guys, time for basics and no waffle.

All figures are approx because I can't be bothered anymore, loosing the will to live, one 21 watt bulb at 12 volts will draw (load) 2 amps, and has a resistance of 6 ohm (Jefrs figures are close enough), two 21 watt in parallel will draw 2 amps each = 4 amps and the resistance drops to 3ohms, (the lower the resistance the greater the load), one bulb blows, back to 6 ohm, 2amps load, half the load and double the resistance of two bulbs, simple no?.

There are different types of load in electronic circuits the main ones being, resistive load, capacitive load and inductive load, to name the three main ones, there are other more complex ones to take account of when designing electronic circuits, an incandescent bulb has a resistive load.

This is my final say on this topic, if you don't understand then I am sorry, I can't make it any simpler, as I said in a previous post I spent my entire working life in electronics, you choose who is correct, frankly I don't care.

[Beezabryan]

You're probably right Peter

[Scalyback]