MCQ
In Fig., assuming the diodes to be ideal:
  • A
    $D_1$ is forward biased and $D_2$ is reverse biased and hence current flows from $A$ to $B$.
  • $D_2$ is forward biased and $D_1$ is reverse biased and hence no current flows from $B$ to $A$ and vice versa.
  • C
    $D_1$ and $D_2$ are both forward biased and hence current flows from $A$ to $B.$
  • D
    $D_1$ and $D_2$ are both reverse biased and hence no current flows from $A$ to $B$ and vice versa.

Answer

Correct option: B.
$D_2$ is forward biased and $D_1$ is reverse biased and hence no current flows from $B$ to $A$ and vice versa.

A symbol of the diode is represented like this: In this problem first we have to check the polarity of the diodes. $-10$ is the lower voltage in the circuit. Now $p-$side of $p-n$ juction $D_1$ is connected to lower voltage and $n-$side of $D_1$ to higher voltage. Thus $D_1$ is reverse biased. Now, let us analyse $2^{\text {nd }}$ diode of the given circuit. The $p$-side of $p-n$ junction $D_1$ is at higher potential and $n$-side of $D_2$ is at lower potential. Therefore $D_2$ is forward biased.

Hence, current flows through the jucntion from $B$ to $A.$

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