basic question about resistance and Ohm's law

[Phil Allison]

<[email protected]>

I think I understand now. Thank you. Too bad there is not an electronic
equivalent to a water pipe faucet. It just reduces the flow without wasting
energy (water) while a resistor does waste power instead of just making it
harder for current to flow through, preserving the rest of the power in the
battery, rather than wasting it by turning it into heat.


** The OP reminds me of a guy I met in a components store once.

On being informed that rechargeable NiCd cells were only 1.2 volts each, not
1.5V, he exclaimed.

" That's ridiculous - how stupid are they not to make them the same. "




..... Phil

 

[John Devereux]

<[email protected]>

I think I understand now. Thank you. Too bad there is not an electronic
equivalent to a water pipe faucet. It just reduces the flow without wasting
energy (water) while a resistor does waste power instead of just making it
harder for current to flow through, preserving the rest of the power in the
battery, rather than wasting it by turning it into heat.


** The OP reminds me of a guy I met in a components store once.

On being informed that rechargeable NiCd cells were only 1.2 volts each, not
1.5V, he exclaimed.

" That's ridiculous - how stupid are they not to make them the same. "

Hey, I broke the legs off my first transistor, then tried to replace it
by wiring together two diodes

 

[John Devereux]

Everybody has done that. The younger you were, the more credit you get.

Hmm... when I posted I had it in my head that it was early teens.

But thinking about it a bit more, must have been earlier, like 9 or
10. Precocious little brat.

It was one of those "101 circuit projects" kits with a solderless
breadboard and a grand total of two 2N-somethings.

 

[Uwe Hercksen]

Along those lines, if I run a 6V circuit with a 6 Ohm bulb (pretending bulbs are linear resistors) it would consume 6W. If I want to power the same bulb by a 12V battery I would have to add a 6Ohm resistor to have the bulb illuminate at the same brightness. This circuit would consume 12W of power. That seems like an incedible waste of power. What am I missing here?

Hello,

you may connect two 6 V bulbs in series to a 12 V source. Each bulb
consumes 6 W, both together 12 W. 1 A flowing thru a 12 Ohm resistor on
a 12 V source gives 12 W. You get twice the light as from one bulb only.
But you can also use a 12 V 6 W bulb, 0.5 A is flowing and the power is
6 W, the resistance is 24 Ohms. You (hopefully) get the same light from
a 6 V 6 W bulb and from a 12 V 6 W bulb.

Bye

 

[tm]

<[email protected]>

I think I understand now. Thank you. Too bad there is not an electronic
equivalent to a water pipe faucet. It just reduces the flow without
wasting energy (water) while a resistor does waste power instead of just
making it harder for current to flow through, preserving the rest of the
power in the battery, rather than wasting it by turning it into heat.


** The OP reminds me of a guy I met in a components store once.

On being informed that rechargeable NiCd cells were only 1.2 volts each,
not 1.5V, he exclaimed.

" That's ridiculous - how stupid are they not to make them the same. "




.... Phil

There's one like that in every Radio Shack. They are usually behind the
counter.

 

[josephkk]

Everybody has done that. The younger you were, the more credit you get.

Not everyone; i never did. But before age 10 i knew better.

?-)

 

[Asad Habeeb]

Tim Wescott

Wescott Design Services

http://www.wescottdesign.com

Nice explanation sir!