Answer:
using a stronger permanent magnet
increasing current in the electromagnet
decreasing the distance between the magnets
Explanation:
As we know the working of magnet is such that when current flows in the coil then due to strong magnetic field the coil will have tendency to rotate.
This is due to the torque on the coil which is given by
now if we need to make the motor to be more strong then we need more torque on it which will be increased by
B = due to stronger magnet or by placing the magnets more closer to each other
i = by increasing the current in the coil