Calculate Equivalent Resistance Of Following Combinations Of Resistors R1 R2 R3 R4

Calculate the equivalent resistance of the following combinations of resistors r1, r2, r3, r4.

Answers:

Since r₃ and r₄ are in parallel   

∴ Equivalent resistance R₁ of this combination is given by

1/R₁ = 1/r₃ + 1/r₄ = r₄ + r₃/r₃r₄

Or R₁ = r₃r₄/r₃ + r₄

Now r₁, r₂ and R₁ are in series

∴ Equivalent resistance R of the whole combination is

R = r₁ + r₂ + r₃r₄/r₃ + r₄ = (r₁ + r₂)(r₃ + r₄) + r₃r₄/r₃ + r₄ Ω