How can I learn to find and add reciprocals? Fractions.

Question

This is related to my electrical class. Parallel and series circuits. 

Answer 1

In a parallel circuit, the sum of the reciprocal resistance is the reciprocal of the total resistance.

 

1 / R_eq = (1 / R₁) + (1 / R₂) + (1 / R₃)

 

 

When adding fractions, you need to find LCD.  The LCD here is R₁R₂R₃.

 

1 / R_eq = (R₂R₃ + R₁R₃ + R₁R₂) / (R₁R₂R₃)

 

 

Then take the reciprocal of the sum over product to get R_eq.