I've included (hopefully it will work this time!) a diagram of two simple circuits. The objective here is to test/verify Ohms law.
Circuit 1 consists of a 5V source, a 680 ohms resistor and a 5mm green LED. Current was measured with a Fluke 87V to be 4.44 mA. Using Ohms law, E=IR, I divided 5V by 0.0044 Amps and got a total resistance of 1136 Ohms.
Next, in circuit2 I introduced a potentiometer with unknown resistance into the circuit. I measured the total current and got 2.76 mA. Again, applying Ohms law I divided 5V by 0.00276 A and got 1811 Ohms for total resistance.
Subtracting Resistanceinitial (1136 Ohms) from Resistancefinal (1811 Ohms) I got 675 Ohms which, by my understanding, should be the resistance setting of the potentiometer.
However, measuring resistance across the pot's terminals I got a reading of 433 Ohms!?
What am I doing wrong?
** EDIT:
I just tried the same experiment using a regular (second) resistor in place of the pot. I guess my math must be wrong because the way I did it, I got the wrong answer again for the 2nd resistor value.
Circuit 1 consists of a 5V source, a 680 ohms resistor and a 5mm green LED. Current was measured with a Fluke 87V to be 4.44 mA. Using Ohms law, E=IR, I divided 5V by 0.0044 Amps and got a total resistance of 1136 Ohms.
Next, in circuit2 I introduced a potentiometer with unknown resistance into the circuit. I measured the total current and got 2.76 mA. Again, applying Ohms law I divided 5V by 0.00276 A and got 1811 Ohms for total resistance.
Subtracting Resistanceinitial (1136 Ohms) from Resistancefinal (1811 Ohms) I got 675 Ohms which, by my understanding, should be the resistance setting of the potentiometer.
However, measuring resistance across the pot's terminals I got a reading of 433 Ohms!?
What am I doing wrong?
** EDIT:
I just tried the same experiment using a regular (second) resistor in place of the pot. I guess my math must be wrong because the way I did it, I got the wrong answer again for the 2nd resistor value.
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