The motor effect and electric motorsIB MYP Physics: Mind map

Exam questions on The motor effect and electric motors

1. In a demonstration in Istanbul, a copper rod rests on two horizontal metal rails between the poles of a strong horseshoe magnet. When a current from a d.c. supply is passed through the rod, the rod rolls along the rails.
   State two changes that would increase the force on the rod.2 marks
2. A straight horizontal wire passes at right angles between the poles of a large magnet. The north pole is on the left and the south pole is on the right, so the magnetic field points to the right. The conventional current in the wire flows away from the observer.
   The poles of the magnet are swapped and the current is also reversed. State the direction of the force on the wire and explain your answer.2 marks
3. Students in Nairobi build a model d.c. motor. A rectangular coil of wire is placed between two magnets and connected to a battery through a split-ring commutator and carbon brushes.
   Explain why the coil starts to turn when the battery is connected.3 marks