Series Circuits

Voltage and current

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series circuits

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

V = V₁ + V₂ + ... + V_n (1)

where

V = applied voltage from the battery or source (Volts)

V_1..n = voltage each resistor (Volts)

V_n = I_n R_n (2)

where

I_n = current (Amps)

R_n = resistance (Ohms)

Since in a series circuit

I₁ = I₂ = .. = I_n (3)

equation (1) can be modified to

R = R₁ + R₂ + .. + R_n (4)

where

R = total circuit resistance (Ohms, Ω)

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

9 12 8