Two identical ideal diodes are connected to an ammeter and a d.c source (1 volt) as shown. In which one of the following circuits, ammeter will not show any deflection?
Show Hint
In a series loop, a single reverse-biased diode is enough to completely block the current. Always look for the configuration where a diode's blocking line ($n$-side) directly faces the incoming positive current flow from the battery source without any alternative parallel paths.
Step 1: Understanding the Question:
The question asks us to identify which of the four diode circuit configurations labeled (a), (b), (c), and (d) will prevent electric current from flowing through the loop, resulting in zero deflection on the ammeter.
Step 2: Key Formula or Approach:
An ideal diode acts as a one-way electrical switch:
1.
Forward Bias: When the anode ($p$-side, triangle base) is at a higher potential than the cathode ($n$-side, straight line), the diode conducts current with zero resistance.
2.
Reverse Bias: When the cathode ($n$-side) is at a higher potential than the anode ($p$-side), the diode blocks current completely, acting like an open switch with infinite resistance.
For a single loop series circuit, if even one component acts as an open switch, no current can flow through the entire branch.
Step 3: Detailed Explanation:
Let's analyze the standard series arrangement represented in configuration (a):
In circuit diagram (a), the two ideal diodes are wired in series along the single loop branch, but they are oriented in opposing directions relative to each other, or connected such that one diode has its $n$-side facing the positive terminal of the 1V d.c. source.
Because this diode is reverse-biased, it introduces infinite resistance into the loop, acting like a broken wire.
Since the components are arranged in series, this blocking effect stops all charge carriers from circulating through the circuit. As a result, the current drops to zero, and the ammeter shows no deflection.
In contrast, the other configurations contain parallel paths or correctly aligned forward-biased orientations that allow current to bypass or flow through the meter.
Step 4: Final Answer:
The ammeter will not show any deflection in circuit (a), which corresponds to option (B).
