Which circuit will not show current in ammeter ?

Options

A.
B.
C.
D.

Answer

To determine which circuit will not show current in the ammeter, we need to analyze each circuit option provided. Let's go through the steps systematically.

### Step-by-Step Solution:

1. **Understanding the Circuit Components**: Recognize that diodes have two terminals: anode and cathode. A diode allows current to flow in one direction (forward bias) and blocks it in the opposite direction (reverse bias).

2. **Analyzing Option 1**:
- In this circuit, we have two diodes connected in series.
- The first diode is reverse biased (anode connected to the negative terminal and cathode to the positive terminal).
- The second diode is forward biased (anode connected to the positive terminal and cathode to the negative terminal).
- Since one diode is reverse biased, it will not allow current to flow through the circuit, making it an open circuit.
- **Conclusion for Option 1**: No current flows; hence, the ammeter will show zero current.

3. **Analyzing Option 2**:
- This circuit has two diodes connected in series, both in forward bias.
- Both diodes will conduct electricity as they are oriented correctly.
- **Conclusion for Option 2**: Current will flow; the ammeter will show current.

4. **Analyzing Option 3**:
- Here, two diodes are connected in parallel, both with the same polarity.
- Both diodes are forward biased and will conduct electricity.
- **Conclusion for Option 3**: Current will flow; the ammeter will show current.

5. **Analyzing Option 4**:
- In this circuit, two diodes are connected in series but with opposite polarities.
- One diode is forward biased while the other is reverse biased.
- The forward biased diode will conduct, while the reverse biased diode will block current.
- **Conclusion for Option 4**: Current will flow through the forward biased diode; the ammeter will show current.

6. **Final Conclusion**: After analyzing all options, only Option 1 does not allow current to flow due to the reverse bias of one of the diodes. Therefore, the circuit that will not show current in the ammeter is Option 1.

### Final Answer:
**Option 1 is the correct answer; it will not show current in the ammeter.**