Electronics · Capacitors and coils / Principles and inquiry
DC motor experiment guide
Watch the role of the commutator and how back EMF sets the rotational speed.
How does it work?
The commutator maintains torque direction; back EMF reduces the current.
Key relationship
Jω′ = kI−bω−τload · I = (V−kω)/R
Try this investigation
- Watch the role of the commutator and how back EMF sets the rotational speed.
- Run and record each of the three baseline presets.
- Compare the changed variable and its result with the baseline records.
Interpreting your results
With a 6 V supply, 0.968 A current and 5 Ω resistance, what is the back emf?
About 1.16 V
Assumptions and limitations
The field and coil are ideal and bearing friction is viscous. Without a commutator the simple model starts at π/4. Experiment on screen; do not reproduce this with real power supplies, outlets or high voltage.