Motor and generator
The same coil and magnet, yet energy is converted in opposite directions.
In a motor, a current-carrying coil in a magnetic field is pushed by the magnetic force and turns; the commutator reverses the current every half turn so the coil keeps turning the same way. In a generator, the coil turns in the magnetic field and cuts the field lines, producing an induced current; the current from an AC generator reverses direction periodically. The stronger the field and the more turns on the coil, the larger the torque or the induced emf.
Torque on the coil vs. time
The commutator reverses the current every half turn, so the torque always acts the same way and the coil keeps turning.
Think about it
Motors and generators are built in very similar ways. How do their energy conversions differ?
A motor converts electrical energy into mechanical energy: a current-carrying coil in a magnetic field is pushed by the magnetic force and turns. A generator converts mechanical energy into electrical energy: a coil turning in a magnetic field produces an induced current. Switch between the two modes and compare the power supply and the ammeter in the circuit.
Model assumptionsCoil area 10 cm × 10 cm · motor current 1 A · generator turns 2 rev/s · motor speed illustrative only
Data log
Set the parameters and click “Record data”. Record several rows with different parameters to plot their relationship and fit a straight line; pause and record at different times to study how a reading changes with time.