Question

As the switch $S$ is closed in the circuit shown in figure current passed through it is:

• A. $4.5A$
• B. $6.0A$
• C. $3.0A$
• D. $zero$

Answer 1

The correct option is A $4.5A$

Let $V$ be the potential of the junction as shown in figure.

Applying junction law, we have

or $\frac{20-V}{2}+\frac{5-V}{4}=\frac{V-0}{2}$

or $40-2V+5-V=2V$ or $5V=45\Rightarrow V=9V$

$\therefore i_3=\frac{V}{2}=4.5A$