Question

Two diodes with zero resistance in forward bias and infinite resistance in reverse bias are connected to a battery as shown in the circuit. Then the value of current \(i\) is: 

 

• A. zero
• B. 0.5 A
• C. 0.4 A
• D. 0.75 A

Hint:

When dealing with ideal diodes in circuits, remember they behave like switches: zero resistance when forward biased and open circuit otherwise.

Answer 1

The Correct Option is B

Given:
- \(D_1\) and \(D_2\) are ideal diodes (zero resistance in forward bias, infinite in reverse).
- Battery voltage = 10 V.

Since diodes conduct only in forward bias:
- Current flows through the diodes that are forward biased.

The two branches have resistors of 20 \(\Omega\) and 40 \(\Omega\) respectively in parallel.

Equivalent resistance, \(R_{eq}\) is:
\[ \frac{1}{R_{eq}} = \frac{1}{20} + \frac{1}{40} = \frac{2+1}{40} = \frac{3}{40} \implies R_{eq} = \frac{40}{3} \approx 13.33\, \Omega \]

Current, \(i = \frac{V}{R_{eq}} = \frac{10}{13.33} = 0.75\, A\).

However, considering diode orientation in circuit and ideal diode behavior, only one diode will conduct effectively allowing current of 0.5 A through 20 \(\Omega\) branch. So, the effective current is 0.5 A.