Question

If two resistor of 25 ohms and 15 ohms are joined together in series and then placed in parallel with 40 ohms resistor the effective resistance of the combination

Answer 1

Answer:

The effective resistance of the combination is 20Ω.

Explanation:

Case: I

When the resistors are connected in series the effective resistance is given as,

$R_s=R_1+R_2$              (1)

R₁=25Ω

R₂=15Ω

By putting the value of R₁ and R₂ in equation (1) we get;

$R_s=25+15=40\Omega$       (2)

Case: II

When the resistors are connected in parallel the effective resistance is given as,

$\frac{1}{R_p}=\frac{1}{R_a}+\frac{1}{R_b}$          (3)

As per the question, the resultant of the series combination is connected in parallel with 40 ohms resistor the effective resistance of the combination is,

$\frac{1}{R_p}=\frac{1}{40}+\frac{1}{40}=\frac{2}{40}=\frac{1}{20}$

$R_p=20\Omega$

Hence, the effective resistance of the combination is 20Ω.

Your question is incomplete, but most probably your full question was"If two resistors of 25 ohms and 15 ohms are joined together in series and then placed in parallel with 40 ohms resistor. Find the effective resistance of the combination."