Question

In the circuit of figure, treat diode as ideal, current in the $4\Omega $resistor is:

A. $2A$
B. $3A$
C. $12/7A$
D. $30/13A$

Answer 1

Hint: First thing important is to notice the nature of the diode, whether it is forward or reverse biased.This will govern the role of the branch of the diode. Then treat the diode as a resistor.

 Complete step-by-step solution:As both the diodes are forward biased, therefore both will act as short circuited.
Then, the
$
  {R_{eq}} = (2||3) + 4 \\
  {R_{eq}} = \dfrac{{2*3}}{{2 + 3}} + 4 = \dfrac{{26}}{5}\Omega \\
 $
Now the equivalent circuit would be

Current through the $4\Omega $resistor will be:
$
   = V/{R_{eq}} \\
   = 12*5/26A \\
   = 30/13A \\
 $

Note:- The main part is the role of diode which should be identified very carefully. Then the equivalent resistance should be found by proper techniques which will heavily reduce the margin of error for any further step.