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Okay, for this setup here I have a simple circuit. I have a
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battery a 9-volt battery with the power supply going to this positive rail of the breadboard
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this orange jumper wire going to the center pin of the slide switch
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I have this blue LED It's anode on the far right pin of this slide switch and the cathode of the LED of the LED going to this
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1,000-oam resistor and the other end of the resistor going into the negative
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rail going back to the negative of the battery so we're going to check the voltage
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the voltage first I'm going to use these two jumper wires here and I'm going to
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place the orange one at the positive end and I'm going to place the black one at the
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negative end and what we could do is I'm gonna go ahead and turn the switch on and we
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see the blue LED turns on I taking my red lead which we gonna be measuring volts you can see the V here on the multimeter I going to place it on the orange lead because this orange
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lead is on our positive end and I'm going to attach the black lead of the
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multimeter to the black jumper wire going to ground or the negative of our
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power supply. So now since I I'm using a 9 volt battery, I need to use a reading on the volt meter that's higher than 9 volts
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So the closest value on this multimeter to 9 volts that's higher than 9 volts is 20 volts
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So I'm going to turn the knob from off to 20 volts
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And right now I got a reading of 9.08 volts or 9.08 volts
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So that's the reading across the power supply here on the circuit
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So now I going to remove the jumpers from the jumpers of the multimeter from these two jumper wires And I want to see how much a voltage drop is across this blue LED So on the anode of the LED I placing the red lead from the multimeter and on the cathode of the LED I placing a reading of 2 volts
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So I'm going to turn my calculator on and I'm going to type in 2.74
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Now I'm going to release these and I'm going to measure the voltage across the resistor now
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So I'm going to place the black lead on this end, on the negative end of the resistor
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or the lead that's on the negative rail here and I'm going to place the red..
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lead from the multimeter to the resistor. On the other side of the resistor connected to the cathode of the LED
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And right now I'm getting a reading of 6.32 volts or 6.32 volts
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So I going to press plus 6 volts And I going to hit enter and I get 9 volts That was about how much I originally read
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So if I put these back on to the leads here, I get 9.07 volts or almost 9.06 volts, which is what I'm getting in our calculation here
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So remember, in a series circuit, a series circuit acts as voltage divider. So the only thing that we have in our circuit here is an LED and a resistor
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Of course we have the switch here, but in theory there's no voltage drop across this switch
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and all of the voltages are being dropped, all of the voltage is being dropped across the LED
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and the resistor. So part of it was across the LED which we measured to be 2.74 volts and
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And part of the voltage drop was across the resistor, which was 6.32 volts is what we measured
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And if we add those two together, the two voltage drops, we get 9.06 volts, which is the
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voltage reading across the power supply itself
