A generator manufacturing company accidentally made an AC generator instead of a DC generator. To fix this error,

Analysis of the Question

This question tests your understanding of the fundamental construction differences between an Alternating Current (AC) generator and a Direct Current (DC) generator. You are asked to identify the specific component change required to convert an AC output into a DC output.

Concept Explanation

• AC Generator: Uses slip rings (two continuous metal rings). As the armature rotates, the current flows in one direction for half a turn and the opposite direction for the other half, resulting in an alternating current.
• DC Generator: Uses a split-ring commutator (a single ring split into two halves). The split-ring commutator acts as a mechanical rectifier. As the coil rotates, the split rings reverse the connections to the external circuit at the exact moment the current in the coil reverses. This ensures that the current flowing through the external circuit always moves in the same direction, producing direct current.

Step-by-Step Solution

1. Identify the current setup: The company currently has an AC generator, which uses slip rings.
2. Identify the goal: The company wants a DC generator.
3. Determine the necessary change: To convert the output to DC, the alternating current must be rectified. This is achieved by replacing the slip rings (which maintain the alternating nature of the current) with a split-ring commutator.
4. Evaluate the options: • Option A (Magnetic field strength) affects the magnitude of the induced EMF, not the direction/type of current. • Option B (Slip rings) is what the generator already has; this would keep it as an AC generator. • Option C (Number of turns) affects the magnitude of the voltage, not the type of current. • Option D (Split rings) correctly identifies the component needed to rectify the current into DC.

Conclusion

Replacing the slip rings with a split-ring commutator is the standard engineering procedure to convert an AC generator into a DC generator.

Exam Tip: Remember the mnemonic "DC = Split" (Direct Current uses a Split-ring commutator) and "AC = Slip" (Alternating Current uses Slip rings). This simple trick will save you time in the exam hall!