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I have a 9 volt battery and I need to use it to run a 3 volt circuit, and I'm not sure what resistor to use. Also, I have a 6 volt battery that I need to use to run a 3 volt circuit. Does anyone know what color codes of resistors I'm supposed to use for each? Any help is much appreciated.

2007-02-16 16:38:16 · 4 answers · asked by mike_gaerheart 2 in Science & Mathematics Engineering

4 answers

It all depends on what the current draw of your load is. If you know that, the current times the resistance value would give you the voltage drop across the resistor. It's a very inefficient way to run your three volt circuit off though. In case one, you're dumping two times the power into your resistor and in case 2, the same power that your actual load circuit is using. Buy two D, C, AA or AAA cells and use them in series to get 3 volts.

2007-02-16 16:53:25 · answer #1 · answered by Gene 7 · 0 0

You need the current draw I when your 3V circuit is supplied with 3V.
For the 9 volt battery,
Vs = IR + Vl
R = (Vs - Vl)/I = (9 - 3)/I = 6/I

For the 6 volt battery,
R = (6 - 3)/I = 3/I

2007-02-16 17:37:57 · answer #2 · answered by Helmut 7 · 0 0

connect three 3ohm resisters across your 9volt battery,so that current will remain at 1amp,now the voltage at each resister is 3volts,let the time taken to discharge the battery be xhours.Now rearrange the ckt by connecting only one 3ohm resister to 9volt battery,now check the time of discharge,it will take exactly 3xhours to discharge.By this we know that 3volt ckt is nothing but 3ohm resister.The same principle can be applied to 6volt battery also

2007-02-16 21:33:11 · answer #3 · answered by 123j 1 · 0 0

I can't believe the answers that some people give. Do they feel they have to answer every thing regardless of how uninformed they are?
You have to know how much current the device draws before you can determine the resister value.

2007-02-20 03:42:03 · answer #4 · answered by H.C.Will 3 · 0 0

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