Friction acts inside machines, not just between surfaces you can see. In a DC motor, spinning parts rub against each other, slowing them down and wasting energy as heat. Larger motors have bigger moving parts — and more rubbing means greater friction losses.

Not all the power a motor consumes does useful work. Some of it fights internal friction, converting energy into heat instead of motion. To measure that loss, you run four DC servomotors — ranging from 30 watts to 100 watts — with no load, measuring the input voltage and current. Then you switch off the power and time how long each motor takes to stop. Bigger motors have larger moving parts, and as the data shows, they lose more energy to friction — because larger moving parts consume power faster, even when the motor isn't doing any work.

The current flowing into a motor tells you how hard it is working, even when it has nothing to drive. You run four DC servomotors — ranging from 30 to 100 watts — with no load, measuring the voltage and current at each motor's input with a multi meter and an ammeter. Then you cut the power and time how long each motor takes to stop. Bigger motors have larger moving parts and more friction, so more charged bits must flow through the wire to keep them spinning. That extra current shows up directly in the input power measurement.

Every DC motor converts electric current into rotational motion through magnetic force, but some energy is always lost fighting internal friction. To measure how much, you run four DC servomotors with no load, ranging from 30 watts to 100 watts. You measure the voltage and current going in, then switch off the power and time how long each motor takes to stop. From the input power and stopping time, you calculate the friction loss. Bigger motors have bigger moving parts — and the results show they lose more energy to friction rather than producing useful rotation.