Does a resistor not effect voltmeter readings?

Question

I'm doing a LED light project for my computer desk and I found a whole bunch of LED's to use, I noticed some of them had a lower voltage rating than 3.2 so I got some resistors and measured the voltage of my AA battery pack with a series of resistors I had, and I realized none of them blocked anything. So I got out a nine volt to see if that might help and again the volt meter showed no difference with a 1k Olm .5 Watt resistor, so does that mean the resistor will have no effect on the power readings or what's going on? I tried 2 of the same type and they did nothing at all to the power readings.

Answer 1

with most LEDs the goal is to limit current to around 20 mA. If you have a 5 volt source this would be 5/.020 = 250 ohms. so you would need a 250 ohm resistor in series with the LED to properly limit the current.

Answer 2

Alex. if you put the resistor directly across the battery, either one of them, and then read the voltage, you are in fact reading directly across the battery terminals. To see the resistor effect, use 2 resistors, and measure across just one of them. You could also put a resistor in series with 1 lead of a LED. Connect the other lead, observing polarity, of course, of the LED to the proper battery terminal, and the other lead of the resistor to the other battery terminal. Now read the voltage across the LED leads. The only way that you'll see any kind of current indication from your meter is to put it in the Amps range (Milli-Amps) and connect the meter in series with the battery and resistor.

Look carefully at your earlier efforts. Where did you connect the resistor across the battery, and where did you place the meter leads. Were the meter leads, electrically, across the battery? Yes they were and the only way to see an effect from the resistor is to leave everything connected while the resistor slowly pulls the battery voltage down, as the resistor discharges the battery.

Answer 3

your wording of the question is obscure.

How can you measure voltage with resistors?

"blocked anything"?

After rereading several times, this is my interpretation:

"You put some resistors across an AA battery, and the voltage out of the battery didn't change". No, it would not, until you used a small resistor and overloaded the battery.

Then you switched to a 9v battery and the same thing happened. Same answer.

Resistors in parallel will draw current by ohms law, I = E/R. The battery voltage will not change unless it gets overloaded.

"Power reading"? what did you use to measure power.

You need to do some reading on electricity to get the terms correct.

.

Answer 4

No it does not

Answer 5

I don't follow your qestion.  Power is I sqaured * R.  Nothing more

Answer 6

when using a resistor(s) when making up a LED array its purpose is to limit current(amps), not voltage. At a given required LED voltage, the resistor limits the LEDs ability to draw excess current and burn itself out.  check out this site to calculate different resistor needs.  http://led.linear1.org/1led.wiz

Answer 7

depends on whether your resister was in series with your power source or parallel..a rheostat is a form of resistance and affects the voltage...same with a potentiometer