when the speed of a dc motor increase the armature current

Options

A. increases
B. decreases does not change
C. increases and decreases continuosly
D. increases and decreases continuously

Answer

To solve the question "When the speed of a DC motor increases, what happens to the armature current?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the DC Motor**: A DC motor converts electrical energy into mechanical energy. The armature is the rotating part of the motor, which consists of coils wound around a soft iron core.

2. **Torque and Current Relationship**: The torque (τ) produced by the motor can be expressed as:
\[ τ = N \cdot I \cdot A \cdot B \cdot \cos(\theta) \]
where:
- \(N\) = number of turns in the coil,
- \(I\) = armature current,
- \(A\) = area of the coil,
- \(B\) = strength of the magnetic field,
- \(\theta\) = angle between the magnetic field and the area vector.

3. **Power and Velocity Relationship**: The power (P) developed by the motor can be expressed as:
\[ P = τ \cdot ω \]
where \(ω\) is the angular velocity (related to speed).

4. **Torque and Speed Relationship**: From the relationship between torque and power, we can derive that:
\[ τ \propto \frac{1}{V} \]
where \(V\) is the speed of the motor.

5. **Current and Speed Relationship**: Since torque is directly proportional to the armature current \(I\), we can conclude:
\[ I \propto \frac{1}{V} \]
This means that as the speed \(V\) of the motor increases, the armature current \(I\) must decrease.

6. **Conclusion**: Therefore, when the speed of a DC motor increases, the armature current decreases.

### Final Answer:
The armature current decreases when the speed of a DC motor increases.

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