Question

What is the total resistance when four resistors of $20,40,60$, and $80$ respectively are connected in parallel (in ohm)?

• A. $4.4$
• B. $9.6$
• C. $14.8$
• D. $20$
• E. $25.2$

Answer 1

Answer: (B)

$9.6$

Given : $R_1=20\Omega$ $R_2=40\Omega$ $R_3=60\Omega$ $R_4=80\Omega$

Equivalent resistance for parallel combination $\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+\frac{1}{R_4}$

$\therefore$ $\frac{1}{R_{eq}}=\frac{1}{20}+\frac{1}{40}+\frac{1}{60}+\frac{1}{80}$ $⟹R_{eq}=9.6\Omega$