Question

A PMDC motor powered by 12 V DC supply draws negligible current (can be assumed as 0 A ) when no load is attached to the shaft and spins at 5000 RPM. When the shaft is clamped with 12 V DC still connected, the current is increased to 2.4 A. What is the power developed by this motor when it spins at 2000 RPM?

Answer 1

To calculate the power developed by the motor at 2000 RPM, we first find the current at that speed using a proportion. Then, we use the current and the given voltage to calculate the power using the formula P = IV.

Step-by-step explanation:

To find the power developed by the motor when it spins at 2000 RPM, we need to calculate the current at that speed and use it to determine the power.

First, we can assume that the current drawn by the motor is proportional to its speed. We can use this relationship to calculate the current at 2000 RPM by setting up a proportion:

Current at 5000 RPM / Current at 2000 RPM = Speed at 5000 RPM / Speed at 2000 RPM

Since we know that the current at 5000 RPM is 2.4 A, we can rearrange the proportion to solve for the current at 2000 RPM:

Current at 2000 RPM = (2.4 A) * (2000 RPM / 5000 RPM) = 0.96 A

Now we can calculate the power developed by the motor using the formula:

Power = Current * Voltage = (0.96 A) * (12 V) = 11.52 W