Series Circuits

Voltage and current

series circuits

In series circuits the sum of voltages is equal to the applied voltage and can be expressed as

V = V1 + V2 + ... + Vn (1)


V = applied voltage from the battery or source (volts, V)

V1..n = voltage each resistor (volts, V)

From Ohms Law 

Vn = In Rn (2)


In = current (amps, A)

Rn = resistance (ohms, Ω)

Since in a series circuit

I1 = I2 = .. = In (3) 

equation (1) can be modified to

R = R1 + R2 + .. + Rn (4)


R = total circuit resistance (ohms, Ω)

Example - Series Circuit

For a 12 V car battery series circuit with three resistors 1.25 Ω, 0.5 Ω and 1.5 Ω, the total resistance can be calculated as

R = (1.0 Ω) + (0.5 Ω) + (1.5 Ω)

    = 3 Ω

The series circuit current can be calculated as

I = V / R

    = 12 / 3

    = 4 amps

Related Topics

  • Electrical - Amps and electrical wiring, AWG - wire gauge, electrical formulas, motors and units

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