How to Compute Resistor Resistance in an Electronic Circuit

Video Transcript

" Hello! This is Ross on behalf of the expertvillage.com. What happens to resistors in terms of value of resistance in a series circuit whenever series is the one connects after the other. So if we have the second resistor what happens the resistances add together and forms 100 ohms you add 100 ohms that is 200 ohms and current as it flows through the circuit you have voltages that will be dropping the across them. If there is same resistance we will have the same voltage across them in a series circuit. So right now I am connected up here with the voltmeter. I have the negative side of the voltmeter connected to the negative part of the power supply and I am going to ahead just measure the voltage coming in from here and to the circuit and it is read 12 volts. So what do we have here in this series of circuit? I am now measuring what is across the LED. There are 2.11 volts. In a series circuit the voltage is added up to equal the total so if the total is 12 and we subtract 2 volts that is 10 it is a little bit more less than so what be 9.9 so now what I am going to do is measure up here across the resistor. I am going to pull the wire out that I am going to connecting to one side of my meter and I am just going to right up into the bus here. So now it is connected in between where the LED and the resistor connect. So now we are measuring the voltage drop across here on based on the calculation it actually should be 9.9 volts let us see 9.88. Now if you was to go ahead and add another resistor in series here, so I am going to pull this resistor out, oops... I have an open circuit. Now that I have an open circuit no current flows and look at this resistor over here on its own bus, I am going to take it back here and hook it into the LED connection as when I soldered earlier, its no trouble to clean it up. There we go. So the LEDs are on but it is not as bright, but more importantly let us measure. I have voltage across the circuit. Meter probe came off there we go… There we go… 12 volts, now it is measured across one resistor this one and that is 492 and what do I have across the other resistor, 5 volts. The negative sign, I am really concerned about it is negative, because I did not move my connection, my reference point into the lower position towards more of the negative of the supply and therefore it read negative. If I swapped them around polarity that it is picking up, that’s negative that way and it is positive this way and there we are. "