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Understanding basic electrical math for troubleshooting series and parallel circuits

Series and Parallel Circuit

Amps = I (Intensity) (Current)

  • I = E/R
  • The current (Amps)(Intensity) is equal at each load in a series circuit
    • To find the Amps in a series circuit: Combine the total resistance for each load in series (TTL_R = R_a + R_b + R_c ....), divide applied voltage by total resistance (I=E/TTL_R), and current is equal (same) at every load.
  • The current (Amps)(Intensity) varies (I=E/R) for each load in a parallel circuit
Series and Parallel Circuit

Volts = E (Electromotive Force)

  • E = I * R
  • Voltage across a parallel circuit is equal to each load
  • Voltage through a series drops at each load
  • To find Voltage drop through a series circuit:
    • Total R (resistance) of series circuit   | TTL_R = R_a + R_b + R_c
    • Divide V (volts) by total R (resistance) | I = V - TTL_R
    • Left with I (current)
    • Apply I (current) to every R (resistance) per load | V_a = I * R_a, V_b = I * R_b, …
    • At each load Voltage Drop = R (resistance) * I (current)
    • The sum of the voltage drop is always equal to the amount of applied voltage

Color on diagram below depicts voltage weakening and not a comparison of voltage drops.

Series and Parallel Circuit

Ohms = R (Resistance)

  • R = E / I
  • Sum of resistance (3 circuits in example) in parallel is = 1/( (1/X) + (1/Y) +(1/Z) )
  • Sum of resistance (3 circuits in example) in series is = X + Y + Z
Series and Parallel Circuit

Watts = w (Power)

  • W = I * E