Series Circuit

Chapter 4
These are:

A source of voltage.
A load.
 A complete path.

VS + R3 R1 R2 
Because there is only one path, the current everywhere is the same. For example, the reading on the first ammeter is 2. 0 mA, What do the other meters read?
+ 2. 0 mA _ VS _ R1 + 2. 0 mA _ R2 2. 0 mA + _ 2. 0 mA +
The total resistance of resistors in series is the sum of the individual resistors. For example, the resistors in a series circuit are 680? , 1. 5 k? , and 2. 2 k?. What is the total resistance? R1 VS 12 V 680? R2 1. 5 k? 4. 38 k? R3 2. 2 k?
The sum of all the voltage drops around a single closed path in a circuit is equal to the total source voltage in that closed path. KVL applies to all circuits, but you must apply it to only one closed path. In a series circuit, this is (of course) the entire circuit.  Notice in the series example given earlier that the sum of the resistor voltages is equal to the source voltage.
I1= 2. 74 mA I2= 2. 74 mA I3= 2. 74 mA IT= 2. 74 mA R1= 0. 68 k? R2= 1. 50 k? R3= 2. 20 k? RT= 4. 38 k? V1= 1. 86 V P1= 5. 1 mW V2= 4. 11 V P2= 11. 3 mW V3= 6. 03 V P3= 16. 5 mW VS= 12 V PT= 32. 9 mW
The voltage drop across any given resistor in a series circuit is equal to the ratio of that resistor to the total resistance, multiplied by source voltage. Voltage divider Summary R1 15 k? VS + 20 V R2 10 k? What is the voltage across R2? The total resistance is 25 k?.
Applying the voltage divider formula: R2 V2 = ? ? RT ? ? 10 k? ? ? VS = ? ? 20 V = 8. 0 V ? 25 k? ? ? Notice that 40% of the source voltage is across R2, which represents 40% of the total resistance. Electric
Voltage dividers can be set up for a variable output using a potentiometer. In the circuit shown, the output voltage is variable.
VS + 15 V R1 20 k? R2 10 k