Question

FIND THE EQUIVALENT RESISTANCE. PLEASE DO STEP BY STEP

Answer 1

Answer

Equivalent resistance of the circuit = 40 Ω

Given

A circuit having 20 , 40 , 8 , 40 , 12 , 10 , 10 , 20 Ω's

To Find

Equivalent resistance

Key points

When resistors are connected in series ,

Req = R₁ + R₂ + R₃ + ...

When resistors are connected in parallel ,

1/Req = 1/R₁ + 1/R₂ + 1/R₃ + ...

Solution

See circuit carefully ,

Starting from right side of the circuit ,

10Ω , 20Ω , 10Ω are connected in series ,

⇒ R₁ = 10 + 20 + 10

⇒ R₁ = 40Ω

Now , R₁ is  connected in parallel with 40Ω ,

⇒ 1/R₂ = 1/R1 + 1/40

⇒ 1/R₂ = 1/40 + 1/40

⇒ 1/R₂ = 1/20

⇒ R₂ = 20Ω

Now , R₂ is connected in series with 8Ω and 12Ω ,

⇒ R₃ = R₂ + 8Ω + 12Ω

⇒ R₃ = 20Ω + 8Ω + 12Ω

⇒ R₃ = 40Ω

Now , R₃ is connected in parallel with 40Ω ,

⇒ 1/R₄ = 1/R₃ + 1/40

⇒ 1/R₄ = 1/40 + 1/40

⇒ 1/R₄ = 1/20

⇒ R₄ = 20Ω

Now , R₄ is connected in series with 20Ω ,

⇒ R₅ = R₄ + 20

⇒ R₅ = 20 + 20

⇒ R₅ = 40Ω

This is equivalent resistance of the circuit