Which of the following statement is incorrect :

Options

A. Both ac and dc dynamo have a field magnet
B. Both ac and dc dynamo have an armature
C. Both ac and dc dynamo convert mechnical energy into electrical energy
D. Both ac and dc dynamo have slip rings

Answer

To determine which statement is incorrect regarding AC and DC dynamos, let's analyze the characteristics of both types of generators step by step.

### Step-by-Step Solution:

1. **Understanding AC and DC Dynamos**:
- **AC Dynamo (Alternator)**: This device generates alternating current (AC). It uses slip rings to maintain a continuous connection with the rotating armature, allowing the current to alternate direction.
- **DC Dynamo (Generator)**: This device generates direct current (DC). It uses a commutator (split rings) to ensure that the current flows in one direction in the external circuit, despite the alternating nature of the current in the armature.

2. **Components of AC and DC Dynamos**:
- Both AC and DC dynamos have:
- An armature (the rotating part).
- Field magnets (which create a magnetic field).
- Brushes (which make contact with the armature).
- The key difference lies in the type of electrical connections:
- **AC Dynamo**: Uses slip rings.
- **DC Dynamo**: Uses split rings (commutators).

3. **Analyzing the Statements**:
- **Statement 1**: Both AC and DC dynamos generate electricity.
- This statement is correct as both types of dynamos convert mechanical energy into electrical energy.
- **Statement 2**: AC dynamos use slip rings, while DC dynamos use commutators.
- This statement is also correct as it accurately describes the components used in each type of dynamo.
- **Statement 3**: The direction of current in a DC circuit remains constant.
- This statement is correct since the commutator ensures that the current flows in one direction.
- **Statement 4**: AC and DC dynamos have slip rings.
- This statement is incorrect because only AC dynamos have slip rings; DC dynamos have split rings.

4. **Conclusion**:
- The incorrect statement among the options provided is **Statement 4**: "AC and DC dynamos have slip rings." This is false because DC dynamos do not use slip rings; they use split rings (commutators).

### Final Answer:
The incorrect statement is: **"AC and DC dynamos have slip rings."**