Torque in a DC Series Motor

When the current drawn by a DC series motor is increased, it leads to an increase in the torque produced by the motor. To understand this phenomenon, let's break down the relationship between current and torque in a DC series motor.

1. Torque in a DC Series Motor
In a DC series motor, the torque is directly proportional to the armature current (Ia). This means that as the current increases, the torque also increases. The torque equation for a DC series motor is given by:

T = k * Ia

Where:
T is the torque produced by the motor,
k is a constant, and
Ia is the armature current.

2. Increase in Current
In this scenario, the current drawn by the DC series motor is increased from 10A to 11A. Let's calculate the increase in torque as a percentage of the initial torque.

3. Calculation
Let's assume that the initial torque produced by the motor at 10A is T1. So, we have:

T1 = k * 10A

Now, when the current is increased to 11A, the torque produced by the motor becomes:

T2 = k * 11A

The increase in torque can be calculated as:

Increase in torque = T2 - T1
= (k * 11A) - (k * 10A)
= k * (11A - 10A)
= k * 1A

To express this increase as a percentage of the initial torque, we need to divide the increase in torque by the initial torque and multiply by 100:

Percentage increase in torque = (Increase in torque / T1) * 100
= [(k * 1A) / (k * 10A)] * 100
= (1A / 10A) * 100
= 10%

Therefore, the increase in torque expressed as a percentage of the initial torque is 10%.

Conclusion
When the current drawn by a DC series motor is increased, the torque produced by the motor also increases. In the given scenario, the increase in current from 10A to 11A results in a 10% increase in torque. This relationship between current and torque is fundamental to understanding and analyzing the performance of DC series motors.