Final answer:
The statement about single-phase induction motors is true, and the phenomenon of inducing an electric current in a copper tube by dropping a bar magnet through it is also true according to principles of electromagnetic induction and Lenz's law.
Step-by-step explanation:
The statement that induction motors also exist as single-phase induction motors is true. Single-phase induction motors are commonly used in appliances like fans, pumps, and household appliances due to their simple construction and operation. As for the related topic of electromagnetic induction, when you drop a bar magnet through a copper tube, it induces an electric current in the tube due to the change in magnetic flux, confirming that the statement provided is also true. This is in line with Lenz's law, which states that the induced emf and the current it causes will always oppose the change in the magnetic flux that produces them. Therefore, any time there is a relative motion between a conductor and a magnetic field, such as a rotating coil in a generator, there will be an induced emf, commonly referred to as back emf in the context of motors.