Series Circuit Voltage Calculations:

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Voltage(E) Drop-

To find calculate the voltage drop of each resistor in a series circuit you multiply the voltage drop of each resistor by the total amperage going through the circuit. I/R, for example a 100 ohm resistor multiplied by the amperage in the circuit of .030 amps (30mV) equals 3volts.

E = IXR

E =.030 X 100

E = 3V

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3V going through that individual resistor, this formula can be used to find the Vd for each individual resistor in a Series Circuit.

 

Total Voltage Drop- The Total Voltage drop can be found by multiplying the Resistance Total (Rt) by the Amperage total It, for example a circuit that has a Rt of 300 and a It of .030amps (30mA) would have a total voltage drop of 9 volts.

E = It X Rt

E = .030 X 300

E = 9volts

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Another method of finding Total Circuit Voltage drop is to 

Total circircuit voltage drop is equal to the sum of all the voltage drops in that circuit.

 

R1vd + R2vd + R3vd + R....... = Vdt

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Series Circuit Amperage (I) Calculations:

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In order to calculate total Series Amperage, divide Voltage drop Total by Resistance Total (Rt) 

It = Vt /Rt 

For example to find the Total Amperage (It) of a circuit with a Voltage of 5 volts and a Resistance Total Rt of 300 would have  .0166 amps (16.6mA)

I=V/Rt

I= 5v / .0166A (16.6mv)                       

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Note: Amperage I is the same through the complete Series Circuit

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Note: 
When using amperage in calculations remember to convert the milliamps to a decimal of 1 amp.  For intance 20 milliamps is .020 Amps.  To multiply 100 ohms by 20 milliamps it would be 100 X .020 = 2 volts, always move the decimal point 3 places to the left for your calculations

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Series Circuit Resistance Calculations

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Resistance total (Rt), in a Series Circuit can be found by adding the resistance values together : ​

Rt = R1+ R2+R...

For example in a series circuit containing three resistors in series R1=100ohms, R2=200ohms and R3=200ohms. This circuit has a total resistance of 500ohms. 

Rt=R1+ R2 + R3

Rt=100 + 200 + 200

Rt= 500 ohms

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