Question

If the junction diodes $D_1$ and $D_2$ in the given circuit are ideal, then the forward biased resistance and reverse biased resistance is infinity:

• A. 2E
• B. E
• C. $\frac{2E}{3R}$
• D. $\frac{E}{R}$

Hint:

For ideal diodes, forward resistance is 0, and reverse resistance is infinity. Analyze the circuit to determine which diode conducts and calculate the current.

Answer 1

The Correct Option is D

In the circuit, $D_1$ and $D_2$ are in parallel with resistors $R$. 
For ideal diodes: forward resistance = 0, reverse resistance = infinity. 
If $D_1$ is forward biased (anode at higher potential), it conducts, and $D_2$ is reverse biased (does not conduct). 
The voltage across $D_1$ (and parallel branch) is $E$. 
Current through $D_1$ branch: Since $D_1$ has zero resistance, the resistor $R$ in series with $D_1$ carries the current. 
Total current: $I = \frac{EV}{R} = \frac{E}{R}$ (since $D_2$ branch does not conduct). 
Thus, the current is $\frac{E}{R}$. 
The answer matches option (4).