How to Analyze Series Circuits

CIRCUIT is the arrangement of components in electrical applications requiring the use of current.

Current in Series Circuit is the same amount at the same time in all the series components.

I = I₁ = I₂ = I₃

I = V_A  ÷ the total resistances in series. (I = V_A / R_T)

Resistance in Series Circuit

R_T = R₁ + R₂ + R₃+…+ etc.

R_T = V_A / I

Voltage in Series Circuit

V_A = IR₁ + IR₂ + IR₃

V_A = V₁ + V₂ + V₃ +… + etc

V_A = IR_T

Power in Series

P_T = P₁ + P₂ + P₃

Let’s have an example.

Solve for R₃ =?

Since I = I₁ = I₂ = I₃
Therefore I = 3

R_T = V_A / I

=27V ÷ 3A

R_T=9Ω

R_T = R₁ + R₂ + R₃

R₃ = R_T  – (R₁ + R₂)

R₃ = 9Ω  – (2Ω + 3Ω)

R₃ = 9Ω  – 5Ω

R₃ = 4Ω - Final Answer

Checking Voltage Drops

V₁ = IR₁ = 3A x 2Ω = 6V  

V₂ = IR₂ = 3A x 3Ω = 9V

V₃ = IR₃ = 3A x 4Ω = 12V

V_A = V₁ + V₂ + V₃

V_A = 6V + 9V + 12V

V_A = 27V

Therefore, to Analyze Series Circuits:

First: When the current (I) for one component is known, use this for I in all components, as the current is the same in all parts of the series circuit.

Second: To calculate I, the total Voltage (V_T) can be divided by the total Resistance (R_T), or individual voltage drop can be divided by R.

Third: When the individual voltage drops around the circuit are known, these can be added up to equal to V_T or V_A.

Thank you for reading this post.

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