Question

In the ladder network shown, current through the resistor 3$\Omega$ is 0.25 A. The input voltage 'V' is equal to

• A. 10 V
• B. 20 V
• C. 5 V
• D. $\frac{15}{2}$

Answer 1

Answer: (B)

if current through the resistor 3$\Omega$ is 0.25 A
total resistance of that branch is 6.
same as the the parallel branch because both have same resistance so same current will shared.
so total current from 5$\Omega$ resistance is 0.25+0.25 that is 0.5 A.
total resistance of $5\Omega branch=5+\frac{6\ast 6}{6+6}=8\Omega$
if current through the resistor 8$\Omega$ is 0.5 A
total resistance of that branch is 8.
same as the the parallel branch because both have same resistance so same current will shared.
so total current from 7$\Omega$ resistance is 0.5+0.5 that is 1 A.
total resistance of circuit $=7+\frac{8\ast 8}{8+8}+9=20\Omega$
$V=I\times RV=1\times 20V=20Volts$